Improved process for the production of crude solder

ABSTRACT

Disclosed is a pyrometallurgical process for producing a crude solder from a feedstock selected in terms of its levels of Sn, Cu, Sb, Bi, Zn, As, Ni and Pb, the process comprising at least the steps of obtaining in a furnace a liquid bath of metal and slag, introducing a reducing agent and optionally also energy, separating the crude solder from the slag and removing liquid from the furnace. Further disclosed is a crude solder comprising at least 9.5-69% wt of tin and at least 25% wt lead, at least 80% tin and lead together, 0.08-12% wt of copper, 0.15-7% wt of antimony, 0.012-1.5% wt of bismuth, 0.010-1.1% wt of zinc, at most 3% wt of arsenic, at most 2.8% wt of nickel, at most 0.7% wt of zinc, at most 7.5% wt of iron and at most 0.5% wt of aluminium. The crude solder may readily be further prepared to become suitable as feedstock for vacuum distillation.

FIELD OF THE INVENTION

The present invention relates to the production of non-ferrous metals,in particular tin (Sn) and lead (Pb), possibly in combination with theproduction of copper (Cu), by pyrometallurgy. More particularly, theinvention relates to an improved process for the production of a crudesolder, a metal mixture comprising primarily tin and lead, which isparticularly suitable for the production of high purity tin and/or leadprime products. The present invention further relates to the crudesolder itself and the use thereof in the production of an improvedsolder composition.

BACKGROUND OF THE INVENTION

The materials available as feedstock for the production of non-ferrousmetals typically contain a plurality of metals. Because of the highpurity requirements for the non-ferrous metals when these are used inmost of their high volume applications, the different metals need to beseparated from each other in the production process. The non-ferrousmetal production processes typically contain at least one and usually aplurality of pyrometallurgical process steps in which metals and metaloxides both occur in a liquid molten state, and wherein the metal oxidesmay be separated by gravity as a separate and typically lighter liquidslag from the usually heavier molten metal phase. The slag is usuallywithdrawn as a separate stream from the process, and this separation maylead to the production of a slag as the coproduct from the metalproduction.

The non-ferrous metals may be produced from fresh ore as the startingmaterial, also called primary sources, or from recyclable materials,also known as secondary feedstocks, or from a combination thereof.Recyclable materials may for instance be by-products, waste materialsand end-of-life materials. The recovery of non-ferrous metals fromsecondary feedstocks has become an activity of paramount importance overthe years. The recycling of non-ferrous metals after use has become akey contributor in the industry, because of the continuing strong demandfor such metals and the reducing availability of high quality freshmetal ores. Many of these secondary feedstocks are available in a finelydivided form, for which the possible end-uses are rather limited. Theprocessing of secondary feedstocks typically involves the use ofpyrometallurgical process steps which generate a slag as coproduct.

When producing copper concentrates by pyrometallurgy, any tin and/orlead present has the tendency to become more readily oxidized thancopper, and the oxides thereof then readily move into the supernatantslag. This slag may be separated from the copper-rich molten metal. By asubsequent chemical reduction step, the tin and/or lead in the slag maythen be returned into their metal state, and these metals may then beseparated from the remaining slag as a molten metal mixture which isrich in tin and/or lead, typically containing significant amounts ofboth. These metal streams typically have a lower melting point than thecopper-containing coproducts and are often called “solder”. Besides thetin and lead, these crude solders may contain significant but minoramounts of other metals, such as copper (Cu), antimony (Sb), arsenic(As), bismuth (Bi), iron (Fe), indium (In), nickel (Ni), zinc (Zn),aluminium (Al), germanium (Ge), tellurium (Te), cobalt (Co), manganese(Mn), selenium (Se), silicon (Si), thallium (TI), gallium (Ga), andsometimes also precious metals, albeit usually in much smaller amounts,such as silver (Ag), gold (Au), platinum (Pt), palladium (Pd), ruthenium(Ru), rhodium (Rh), osmium (Os), and iridium (Ir). The crude solder mayalso contain elements which are not considered as metals, such assulphur (S), carbon (C) and oxygen (O).

The crude solders may have direct commercial uses, depending on theircomposition, but they are also known as an intermediate for the recoveryof some of their individual components in a higher purity form, suitablefor producing concentrated metal products that are acceptable forupgrade into their more demanding end-uses. A high interest remainsprimarily in recovering higher purity tin (Sn) from such solder streams,and also in recovering lead (Pb) in some higher purity forms.

U.S. Pat. No. 4,508,565 discloses a method for producing lead having asulphur content of 1.0% wt from pellets formed from oxidic-sulphaticlead raw materials originating from copper-converter dust. The rawmaterial contained 40% wt of lead, 12% wt of zinc, 3.5% wt of arsenic,1.15% wt of copper, 8.0% wt of sulphur, 0.5% wt of bismuth and 0.6% wtof tin. About half of the pellets were charged into a top-blown rotaryconverter of the Kaldo-type, together with finely-divided limestone,granulated fayalite slag obtained from copper manufacturing process andcoke in particle sizes of between 5 and 12 mm. This first furnace chargewas heated with the aid of an oil-oxygen burner to a doughy consistency,upon which the second half of the pellets, further amounts of limestone,fayalite slag and coke were added, and heating was continued. From theconverter were tapped (i) a slag at 1120° C. containing 16.5% Zn, 18%Fe, 1.4% Pb, 1.4% As, 1.5% Sn, 20% SiO₂, 21% CaO and 1.5% MgO, as wellas (ii) the raw lead product containing 1.0% sulphur. U.S. Pat. No.4,508,565 is not concerned with the production of a solder or with therecovery of high purity metal streams therefrom.

A known technique for obtaining higher purity metal streams startingfrom solder, is by vacuum distillation, a technique which is typicallyperformed under very low pressures in combination with relatively hightemperatures. By means of vacuum distillation, lead may be separated byevaporation from other less volatile metals, such as tin. Vacuumdistillation may serve to separate a solder stream into a higher puritylead stream as overhead product, and a higher purity tin stream asleftover bottom product. The vacuum distillation of solder-type metalmixtures may be performed batch-wise or in continuous mode. However, theinventors have found that the distillation of solder-type metals may besuffering from operational problems. Over time, even at hightemperatures, insoluble solids may form by the crystallization ofintermetallic compounds containing copper, nickel, iron and/or zinc.These insoluble solids may adhere to the distillation equipment,particularly in sensitive areas such as small openings, therebyimpairing smooth operations and even blocking the equipment.

The inventors have found that particular metals are capable, undervacuum distillation conditions, of forming mutual intermetalliccompounds between at least two of these particular metals and/orintermetallic compounds of at least one of the particular metals withtin. The inventors have further found that many of these intermetalliccompounds have a much higher melting point than the temperature of themixture in which they are formed. The inventors have therefore foundthat these high melting point intermetallic compounds may come out ofsolution and form solids. These solids may remain suspended in theliquid metal and risk to reduce the fluidity of the mixture, such as byraising the viscosity of the liquid mixture. This already by itself mayhinder a smooth operation of the distillation equipment, such as byslowing down the flow of liquid metals, which reduces the equipmentcapacity and thus force the equipment to be operated at reducedthroughput. The solids may also adhere and/or attach to the distillationequipment, and thereby create a risk for impairing or even obstructingthe operation of the distillation equipment, e.g. by clogging upimportant passages for the process streams. The described phenomenon mayeven lead to unplanned process shutdowns to open the distillationapparatus and either clean or replace the affected equipment items.

The inventors have found that in particular chromium (Cr), manganese(Mn), vanadium (V), titanium (Ti), tungsten (W), copper (Cu), nickel(Ni), iron (Fe), zinc (Zn) and aluminium (Al), are metals of which thepresence in a solder stream which is fed to a vacuum distillation stepmay lead to the disturbing intermetallic compounds. Cu, Ni, Fe, Zn andAl are rather typically present in solder streams from non-ferrous metalproduction, usually because of their presence in the starting materials.Fe and Al may also be introduced as part of process steps upstream ofthe solder production.

The inventors have found that the identified problems may significantlybe alleviated and even may be avoided by controlling within particularlimits the concentration of these metals in the crude solder.

For removing these metals, the crude solder is conventionallypre-treated, upstream of the vacuum distillation, using a fairly complexso-called “cupro process” or “silicon process”, more correctly the“cuprosilicon process”, in which elemental silicon, often also called“silicon metal”, is introduced in a suitable form to react some of themetals (such as copper, nickel and iron) selectively away from the leadand tin, to form metal-silicon (silicide) alloys or intermetalliccompounds. Two immiscible metal phases are then formed whereby thesilicides are retrieved in the top layer, also called the “cupro” layeror material. When the reaction is completed, the temperature is loweredand the “cupro” layer on top of the solder metal phase solidifies firstbecause it has the highest melting temperature. This “cupro” layer maythen be removed from the still molten solder metal phase upon which itfloats, for example by tapping the solder away from underneath thesolidified cupro layer. After being subjected to the silicon process andcooling, the solder contains less copper, nickel, and/or iron and istherefore more suitable for obtaining higher purity metal streams byvacuum distillation. U.S. Pat. No. 2,329,817 discloses such a process inwhich 36 parts by weight of silicon metal was added to 600 parts of amolten impure “white metal”, containing 5.27% Ni, covered with 48 partsof a sodium silicate slag. After the reaction, 74.0 parts by weight of asilicide layer was formed containing 42.5% wt Ni and only minor amountsof Sn, Pb, As and Sb. The remaining 552 parts by weight of metal mixturecontained only 0.13% wt of nickel. However, such a process requires andconsumes rather scarce and hence expensive raw materials containingsilicon metal, which ultimately, after recycling of the silicide formedin the silicon process, end up as oxides in a low value by-product suchas slag. This downgrade of high value silicon metal to the much lowerslag value represents a significant economic burden.

Technically, aluminium could also be used in the cuprosilicon process,instead of—or together with—silicon. The contaminant metals would thenform aluminides, and these would also separate into the cupro layer andmay thus be removed. This is however not done in practice. Aluminiumbrings the problem that with antimony and arsenic, under the conditionsof the cuprosilicon process, it forms aluminium antimonide and aluminiumarsenide. These intermetallic compounds, upon cooling, readily reactwith water, even under standard, normal and/or ambient conditions,whereby the moisture in the ambient air is sufficient, to form thehighly toxic gasses stibine (SbH₃) or arsine (AsH₃), gasses which arelethal at very low concentrations in air. Because it is practically notpossible to avoid these safety risks, the use of aluminium in thecuprosilicon process is not an option and hence excluded.

GB 224923 discloses a treatment of a concentrate of Cornish tin ore toproduce a lead/tin alloy, hence a solder-type of product. The tin oreconcentrate contained at least 15% of tin, further contained arsenicalpyrites, and was having a siliceous gangue as the non-valuable part ofthe concentrate. The tin ore concentrate was first roasted to eliminatethe arsenic and to convert at least a part of the iron sulphide in thepyrite into iron oxide. The roasted tin concentrate was mixed with alead concentrate and the mixture was smelted in a reverberatory furnacein a reducing atmosphere. A considerable excess of lead over the tin waspresent, and the proportion of lead to tin in the charge was preferablyfrom 6 to 8 of lead to 1 of tin. Additional oxide of iron or other fluxmay have been added to make a proper slag. Metallic iron, preferably tinplate scrap, was added for the reduction of the sulphide of lead and tininto the respective metals. The temperature of the charge was graduallyincreased, but was not be allowed to rise as high as that at whichsilicates are formed, until the tin oxide was converted into tinsulphide. When this conversion had happened, the temperature was raisedfurther to form a slag and to complete the reduction of the sulphides oflead and tin. The charge was then skimmed and tapped. A tin-lead alloywas found at the bottom of the bath and this product was consideredsuitable to be used for the production of various alloys of tin andlead, or subjected to any known process for separating more or lesscompletely the two metals. GB 224923 is silent about metals other thanlead and tin that may have been present in the alloy product, such asexcess iron, nor how any lead and/or tin might be separated downstreamfrom the solder-type product, in which the lead to tin ratio was from6:1 to 8:1.

Therefore, there remains a need for a simple and cost effective processto produce a crude type of solder stream, preferably from secondaryfeedstocks which are possibly (partially) finely divided, whereby thecrude solder is sufficiently rich in tin and lead, and sufficiently leanin copper, nickel, iron and zinc, such that the composition is, afteronly relatively simple chemical tuning steps, suitable for trouble-freevacuum distillation to separate lead from tin, more particularly withoutthe risk for the formation in the distillation equipment ofintermetallic compounds caused by the presence of disturbing amounts ofcopper, nickel, iron and zinc, and this without requiring thecuprosilicon process step as an essential extra processing step forconditioning the crude solder to a quality that does not lead to theformation of intermetallic compounds during downstream vacuumdistillation.

A conventional apparatus for producing copper concentrate from coppercontaining secondary feedstocks, whereby crude solder is formed as aby-product, is a top-blown rotary convertor (TBRC), also called aKaldo-type furnace. This is a furnace equipped for rotating around alongitudinal axis but is also equipped for tilting around a secondhorizontal axis perpendicular to that longitudinal axis. However, a TBRCis a complex and expensive apparatus. Furthermore, if part of thefeedstock is finely divided, a major part of this fine portion mayreadily be blown out of the TBRC by the flue gasses that are typicallygenerated inside, before they have a chance to become incorporated intothe liquid bath inside the furnace. This feedstock portion becomes lostfor the process and additionally may create a significant waste disposalproblem. There are alternatives to the TBRC, such as the so-called“Isasmelt” or the “Ausmelt” apparatuses for producing copper concentrateprime product from secondary feedstocks, but these are equally complexapparatuses.

A further need therefore exists to simplify the solder productionprocess such that it may be performed in a much less complex processingequipment, which preferably is also able to accept finely dividedfeedstocks without causing operational or waste disposal problems.

The present invention aims to obviate or at least mitigate the abovedescribed problem and/or to provide improvements generally.

SUMMARY OF THE INVENTION

According to the invention, there is provided a process for producing acrude solder, a crude solder obtainable from the process, and the use ofthat crude solder, as defined in any of the accompanying claims.

In an embodiment, the invention provides a process for producing a crudesolder comprising lead (Pb) and tin (Sn) from a feedstock whichcomprises at least 50% wt of total metal, expressed relative to thetotal dry weight of the feedstock, wherein the total feedstock comprisesthe following metals, the amounts of each metal being expressed as thetotal of the metal present in the feedstock in any oxidized state and inthe reduced metal form, and relative to the total dry weight of thefeedstock:

-   -   at least 2% wt and at most 71% wt of tin (Sn),    -   at least 1.00% wt and at most 10% wt of copper (Cu),    -   at least 0.02% wt and at most 5% wt of antimony (Sb),    -   at least 0.0004% wt and at most 1% wt of bismuth (Bi),    -   at most 37% wt of zinc (Zn),    -   at most 1% wt of arsenic (As), and    -   at most 2% wt of nickel (Ni),        wherein the total feedstock further comprises lead (Pb) and is        characterized by a Pb/Sn weight ratio of at least 0.5 and at        most 4.0,        and wherein at least one of tin (Sn) and lead (Pb) is at least        partially present in an oxidized valence form,        the process comprising the following steps:    -   a) obtaining a liquid bath comprising a molten metal and/or a        molten metal oxide slag in a furnace by introducing at least a        portion of the feedstock into the furnace and melting the added        feedstock portion;    -   b) introducing at least one reducing agent into the furnace and        reducing at least a part of the oxidized valence form of tin        and/or lead into tin and/or lead metal;    -   c) optionally introducing into the furnace at least one energy        source comprising a combustible material and/or at least one        metal which is less noble than Sn and Pb, and oxidizing the        combustible material and/or the at least one metal in the energy        source by the injection of air and/or oxygen into the furnace;    -   d) separating the crude solder obtained in step b) and/or c)        from the slag and removing from the furnace at least a portion        of the crude solder and/or of the slag.

In an embodiment the invention provides a crude solder obtainable by theprocess according to the present invention, comprising, in addition tounavoidable impurities and relative to the total weight of the crudesolder:

-   -   at least 9.5% wt and at most 69% wt of tin (Sn),    -   at least 25% wt of lead (Pb),    -   at least 80% wt of tin (Sn) and lead (Pb) together,    -   at least 0.08% wt and at most 12% wt of copper (Cu),    -   at least 0.15% wt and at most 7% wt of antimony (Sb),    -   at least 0.012% wt and at most 1.5% wt of bismuth (Bi),    -   at least 0.010% wt and at most 1.1% wt of sulphur (S),    -   at most 3% wt of arsenic (As),    -   at most 2.8% wt of nickel (Ni),    -   at most 0.7% wt of zinc (Zn),    -   at most 7.5% wt of iron (Fe), and    -   at most 0.5% wt of aluminium (Al).

In an embodiment, the process according to the present invention is forproducing the crude solder according to the present invention.

The solder composition as specified occurs either as a molten liquidphase at a temperature above 300° C., or as a solid alloy at lowertemperatures. The solid alloy may exceptionally be granulated orpowdered into a particulate material form, in which form it may attractmoisture. For sake of accuracy, the concentrations as specified are insuch context intended to represent values based on the total dry weightof the composition.

The inventors have found that the selection of the process feedstock, inaccordance with how this is prescribed as part of the present invention,allows the process according to the present invention to produce a crudesolder which may readily be further purified or “tuned” by simpleprocess steps into a quality that is suitable for a trouble-freedownstream vacuum distillation for the evaporation of lead from tin inthe solder. The inventors have found that the crude solder obtainablefrom the process according to the present invention contains thepotentially disturbing metals in such concentrations that the complexand expensive “cupro” process step, i.e. a step in which silicon isadded in an oxidisable form to form silicides, which silicides may beseparated from the solder upon cooling, thereby removing a portion ofthe potentially disturbing metals, may be eliminated and skipped fromthe steps preparing the crude solder as feedstock for the vacuumdistillation.

The inventors have found that a proper selection of the feedstock of theprocess according to the present invention allows the production of acrude solder which contains amounts of the metals of concern that may befurther reduced without needing the scarce and expensive raw metalssilicon and/or aluminium. In other words, the crude solder produced bythe process according to the present invention may be furtherconditioned to become suitable as feedstock for vacuum distillation bychemical treatment steps other than a treatment with silicon and/oraluminium metal to form silicides and/or aluminides and the selectivesolidification and removal of these silicides and/or aluminides.

The metals of concern are the metals that may form intermetalliccompounds under vacuum distillation conditions, either with itself, eachother, or with tin. The list of metals of concern particularly includeschromium (Cr), manganese (Mn), vanadium (V), titanium (Ti), tungsten(W), copper (Cu), nickel (Ni), iron (Fe), zinc (Zn) and aluminium (Al).Several of these metals do not need to be considered because they aretypically very scarce in the raw materials for the production of themajor non-ferrous metals that contain lead and/or tin. The crude solderand the raw materials of the process according to the present inventiontypically contain at most 0.10% wt of Cr, Mn, V, Ti or W, preferably atmost 0.05% wt, more preferably at most 0.010% wt, even more preferablyat most 0.005% wt, preferably at most 0.0010% wt, more preferably atmost 0.0005% wt, even more preferably at most 0.0001% wt of any one ofCr, Mn, V, Ti or W, relative to the total dry weight of the composition.The present invention is therefore primarily concerned with the levelsof Cu, Ni, Fe, Zn and Al, because these metals may be rather typicallypresent in solder streams from non-ferrous metal production, usuallybecause of their presence in the starting materials. Fe and Al may alsobe introduced as part of process steps upstream of the solderproduction.

The applicants have found that the crude solder obtainable by theprocess according to the present invention may be properly conditionedor tuned to become a suitable feedstock for vacuum distillation usingthe treatment steps described in our co-pending patent applicationEP-A-16190907.2, which was first filed on 27 Sep. 2016.

The inventors have further found that the possibly harmful metals, andin particular copper, do not need to be removed entirely from the crudesolder in order to make this stream suitable, after further tuning ortreatment as mentioned above, for vacuum distillation. The inventorshave for instance found that the identified problems may be reduced to apractically and economically acceptable level when small amounts ofcopper remain present in the tuned solder that is fed to thedistillation step. This finding brings the advantage that solder streamsmay be processed which occur as the by-product from the recovery ofcopper from primary and/or secondary feedstocks, in particular fromsecondary feedstocks, even more importantly from feedstocks containingend-of-life materials.

The inventors have found that the presence of some sulphur in the crudesolder is advantageous. The sulphur readily helps in the downstreamsteps where Cu is removed from the crude solder, as part of the furthertuning upstream of the vacuum distillation step. With S within theprescribed limits, the applicants have found that the downstream“tuning” of the crude solder is facilitated, and improved by reducingthe amount of chemicals that need to be used.

The inventors have found that more valuable tin may be recovered in thecrude solder when the lead/tin ratio of the feedstock is least 0.5 andat most 4.0. The inventors have found, when the feedstock comprises morelead, that the relative amount of tin in the crude solder relative tothe amount of tin in the feedstock, is also higher. The inventors havefound, by offering more lead together with the tin, that the recovery oftin from the feedstock is improved, and less of the available tin isending up in the slag. The amount of recovered tin is typically thelargest value contributor to the processing of the crude solder. Therecovery of tin is therefore an important process parameter and isadvantageously as high as economically and practically justified.

We have found that the crude solder produced by the process according tothe present invention, after tuning, may readily be subjected to avacuum distillation step without the problem of the formation ofintermetallic compounds during the vacuum distillation.

The inventors have further found that the process according to thepresent invention may readily be carried out in a smelter furnace. Asmelter furnace is a fairly simple and cheap apparatus consisting of alarge cylinder-shaped furnace which only needs to be able to tilt aroundits longitudinal axis over a part of a full circle. This finding bringsthe advantage that the crude solder may be produced by the processaccording to the present invention, for instance as temporary productioncampaigns, in the same smelter apparatus which may also be producing inother campaigns a copper metal phase of at least 70% wt and typically75% wt of Cu, also known as “black copper” and/or in a smelter apparatuswhich also recovers even higher purity copper from such copperconcentrate. Optionally there may be provided a simple washing step inbetween the campaigns, as further detailed below.

The inventors have also found that the process according to the presentinvention is able to accept finely divided feedstocks without anyoperational problems.

The applicants have further found that the reducing agent in step b)and/or step k) may already be introduced together with the feedstockportion added as part of step a) and/or step j).

The applicants have also found that, if extra energy needs to besupplied as part of step c) and/or step l), that this may optionally beperformed together with the introduction of the reducing agent of stepb) and/or step k), and thus possibly also together with the introductionof the feedstock portion of step a) and/or step j).

The applicants have thus found that step b) and step c), as well as stepk) and step l), may be combined, and thus that the reducing agent ofstep b) and/or k) and the energy source of respectively step c) and/orstep l) may be introduced together. This combination of steps may beperformed separate from respectively step a) and/or j), or may becombined with respectively step a) or step j).

The applicants submit that the options offered for steps a)-d) abovealso apply to the corresponding steps j)-m) which are introduced furtherbelow in this document.

The applicants have found that particular materials may act both as areducing agent and as an energy source comprising at least one metalwhich is less noble than Sn and Pb. A very suitable example of suchmaterial is ferrosilicon (FeSi), a material in which both elemental ironand elemental silicon are present. Iron and silicon are both less noblethan Sn and Pb. The elemental iron is able to act as a reducing agent,able to convert SnO₂ and/or PbO into respectively Sn and Pb metal, whilethe iron converts to FeO and/or Fe₂O₃, which oxide moves into the slagphase. The elemental silicon is able to convert SnO₂ and/or PbO into Snand/or Pb, while the silicon itself converts into SiO₂, which also movesinto the slag phase.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE shows a flow diagram of an embodiment of the processaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will be described in the following with respect toparticular embodiments and with reference to certain drawings but theinvention is not limited thereto but only by the claims. Any drawingsdescribed are only schematic and are non-limiting. In the drawings, thesize of some of the elements may be exaggerated and not drawn on scalefor illustrative purposes. The dimensions and the relative dimensions donot necessarily correspond to actual reductions to practice of theinvention.

Moreover, the terms top, bottom, over, under and the like in thedescription and the claims are used for descriptive purposes and notnecessarily for describing relative positions. The terms so used areinterchangeable under appropriate circumstances and the embodiments ofthe invention described herein can operate in other orientations thandescribed or illustrated herein.

As used herein and in the claims, the terms “comprising” and “including”are inclusive or open-ended and do not exclude the presence ofadditional unrecited elements, compositional components, process ormethod steps. Accordingly, the terms “comprising” and “including”encompass the more restrictive terms “consisting essentially of” and“consisting of.”

Unless specified otherwise, all values provided herein include up to andincluding the endpoints given, and the values of the constituents orcomponents of the compositions are expressed in weight percent or % byweight of each ingredient in the composition.

Additionally, each compound used herein may be discussed interchangeablywith respect to its chemical formula, chemical name, abbreviation, etc.

In this document and unless specified differently, amounts of metals andoxides are expressed in accordance with the typical practice inpyrometallurgy. The presence of each metal is typically expressed in itstotal presence, regardless whether the metal is present in its elementalform (oxidation state=0) or in any chemically bounded form, typically inan oxidized form (oxidation state >0). For the metals which mayrelatively easily be reduced to their elemental forms, and which mayoccur as molten metal in the pyrometallurgical process, it is fairlycommon to express their presence in terms of their elemental metal form,even when the composition of a slag or dross is given, wherein themajority of such metals may actually be present in an oxidized and/orchemically bounded form. It is therefore that the feedstock according tothe process according to the present invention and the crude solderaccording to the present invention specify the content of Fe, Sn, Zn,Pb, Cu, Sb, Bi, As, Ni as elemental metals. Less noble metals are moredifficult to reduce under non-ferrous pyrometallurgical conditions andoccur mostly in an oxidized form. These metals typically are expressedin terms of their most common oxide form. Therefore, where necessary,the content of Si, Ca, Al, Na are respectively expressed as SiO₂, CaO,Al₂O₃, Na₂O.

Within the context of the present invention, the expression “less noblemetals than metal X” means the metals that are more prone to undergooxidation under the conditions and in the particular environment of thecontext wherein the expression is used and this to the benefit of beingable to obtain a reduction of the metal X. For example, the expression“metals less noble than Sn and Pb” refers to metals which are, under theconditions and in the particular environment of the context wherein theexpression is used, more prone to oxidation and able to obtain areduction of Sn and Pb.

The metals of interest for this invention have, under the typicalpyrometallurgical furnace conditions of non-ferrous metal processing,affinities for oxygen, and will tend to distribute between the metal andthe slag phase. From lower to higher affinity for oxygen, and hence froma relatively high affinity to a lower affinity for the metal phase, theranking of these metals may be represented roughly as follows:Au>Ag>>Bi/Cu>Ni>As>Sb>Pb>Sn>>Fe>Zn>Si>Al>Mg>Ca. For convenience, one maycall this a ranking of the metals from the more noble to the less noble,but this qualification has to be linked to the particular conditions andcircumstances of non-ferrous metal pyrometallurgical processes, and mayfail when exported into other fields. The relative position ofparticular metals in this list may a.o. be affected by the presence orabsence of other elements in the furnace, such as e.g. silicon.

The equilibrium distribution of metal between metal and slag phase mayalso be influenced by adding oxygen and/or oxygen scavenging materials(or reducing agents) into the liquid bath in the furnace.

Oxygen addition will convert some of the metals in the metal phase intotheir oxidised form, which oxide will then move into the slag phase. Themetals in the metal phase which have a high affinity for oxygen will bemore prone for undergoing this conversion and move. Their equilibriumdistribution between metal and slag phase may thus be more subject tochange.

The opposite may be obtained by adding oxygen scavenging materials.Suitable oxygen consumers may for instance be carbon and/or hydrogen, inwhatever shape or form, such as in organic materials, e.g. plastics,including polyvinyl chloride (PVC), wood, or other combustibles, such asnatural gas. Carbon and hydrogen will readily oxidize (“burn”) andconvert to H₂O and/or CO/CO₂, components that readily leave the liquidbath and entrain its oxygen content from the bath. But also metals suchas Si, Fe, Al, Zn and/or Ca are suitable reducing agents. Of particularinterest are iron (Fe) and/or aluminium (Al), because of their readyavailability. By oxidizing, these components will reduce some of themetals in the slag phase from their oxidized state into their metalstate, and these metals will then move into the metal phase. Now it arethe metals in the slag phase which have a lower affinity for oxygen thatwill be more prone for undergoing this reduction reaction and for makingthe move in the opposite direction.

In a smelter step, one of the purposes is to reduce oxides of valuablenon-ferrous metals that are coming in with the feed into theircorresponding reduced metals. The direction and speed of the reactionsoccurring in the smelter step may additionally be steered by controllingthe nature of the atmosphere in the furnace. Alternatively or inaddition, oxygen donating material or oxygen scavenging material may beadded to the smelter.

A highly suitable oxygen scavenging material for such operations is ironmetal, usually scrap iron being preferred. Under the typical operatingconditions, the iron will react with hot oxides, silicates and the othercompounds of metals having a lower affinity for oxygen than iron, toyield a melt containing the latter metals in elemental form. Typicalreactions include:

MeO+Fe→FeO+Me+heat

(MeO)_(x)SiO₂ +xFe→(FeO)_(x)SiO₂ +xMe+heat

The temperature of the bath remains high through the exothermic heat ofreaction and the heat of combustion. The temperature may readily be keptwithin a range in which the slag remains liquid and volatilization oflead and/or tin remains limited.

Each of the reduction reactions taking place in the melting furnace isreversible. Thus, the conversion realized through each reaction islimited by the equilibria defined in relationships such as thefollowing:

${{K1} = \frac{\lbrack{FeO}\rbrack \lbrack{Me}\rbrack}{\left\lbrack {{Me}O} \right\rbrack \lbrack{Fe}\rbrack}}{{K2} = \frac{{\left\lbrack {({FeO})_{x}{SiO}_{2}} \right\rbrack \lbrack{Me}\rbrack}^{x}}{{\left\lbrack {\left( {{Me}O} \right)_{x}{SiO}_{2}} \right\rbrack \lbrack{Fe}\rbrack}^{x}}}$

In the case where Me is copper, K1 and K2 are high at normal reactiontemperatures and reduction of copper compounds thus proceedssubstantially to completion. In the case of lead and tin, K1 and K2 areboth relatively low, but the copper in the metal phase, if present insufficient quantities, may extract metallic lead and tin from the slagreaction zone, thereby lowering the activities of these metals in theslag and driving the reduction of combined lead and tin to completion.

The vapour pressure of zinc is relatively high at the typical reactiontemperature and a major proportion of zinc, in contrast to lead and tin,may readily be volatilized out of the furnace. Zinc vapours leaving thefurnace are oxidized by air which may e.g. be aspirated between thefurnace mouth and the hood and/or the exhaust pipe. The resultant zincoxide dust is condensed and collected by means of conventional dustcollecting systems.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,more than 50% wt of total metal, preferably at least 51% wt, morepreferably at least 52% wt, even more preferably at least 53% wt,preferably at least 54% wt, more preferably at least 55% wt, even morepreferably at least 56% wt, even more preferably at least 57% wt,preferably at least 58% wt, more preferably at least 59% wt, and yetmore preferably at least 60% wt of total metal, preferably at least 65%wt, more preferably at least 70% wt, even more preferably at least 75%wt.

In an embodiment of the process according to the present invention, thefeedstock further comprises substances or components selected from O andS atoms, e.g. when contained in oxides and/or sulphides, any of thehalogens, carbon, and organic material.

The feedstock comprises a metallic part, i.e. the amount of total metalin % wt, and typically also a non-metallic part which represents theremainder of the feedstock. We have found that the remainder of thefeedstock is preferably primarily selected from O and S atoms containedin oxides and/or sulphides, any halogens, carbon, and/or organicmaterial. The applicants prefer, apart from the metals, that thefeedstock primarily comprises O and S atoms, preferably when containedin oxides and/or sulphides, carbon, or organic material, such as mostkind of plastics including PVC, because the process may readily be madecapable of coping with these additional substances or components, e.g.by providing appropriate exhaust gas treatment facilities. Morepreferably, the feedstock contains, apart from the metals, oxygen, e.g.as part of oxides, carbon and/or organic material, because of the easewith which these may be handled by the process. Most preferably, theapplicants prefer oxygen in the form of metal oxides, because othercomponents may bring emission concerns, e.g. as SO₂ or SO₃, as CO orCO₂, dioxins, etc . . . , and therefore simplify any treatment of thefurnace exhaust gasses.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,more than 2% wt of tin, preferably at least 4% wt, more preferably atleast 6% wt, even more preferably at least 8% wt, preferably at least10% wt, more preferably at least 12% wt, even more preferably at least14% wt, yet more preferably at least 16% wt of tin, preferably at least18% wt, more preferably at least 20% wt, even more preferably at least22% wt, yet more preferably at least 24% wt of tin.

We have found that a higher amount of tin in the feedstock reduces themelting point of the feedstock, with the advantage that the processaccording to the present invention is operable over a wider temperaturerange. We have also found that the high purity tin metal which mayeventually be recovered from the crude solder obtainable by the processaccording to the present invention is higher in demand as compared tothe high purity lead metal. A higher tin content in the process streamsof the present invention thus increases the economic interest in thecrude solder obtainable by the process according to the presentinvention as a further feedstock for recovering tin metal in highpurity.

In an embodiment of the process according to the present invention,feedstock comprises, relative to the total dry weight of the feedstock,less than 71% wt of tin, preferably at most 69% wt, more preferably atmost 65% wt, even more preferably at most 62% wt, yet more preferably atmost 59% wt, preferably at most 56% wt, more preferably at most 53% wt,even more preferably at most 50% wt, yet more preferably less than 50%wt, preferably at most 48% wt, more preferably at most 46% wt, even morepreferably at most 45% wt, preferably at most 44% wt, more preferably atmost 43% wt, even more preferably at most 42.5% wt, yet more preferablyat most 42% wt of tin, preferably at most 41% wt, more preferably atmost 40% wt, preferably at most 38% wt, more preferably at most 36% wt,even more preferably at most 34% wt, preferably at most 32% wt, morepreferably at most 30% wt, even more preferably at most 28% wt of tin.

We have found that a lower amount of tin in the feedstock improves thedownstream separation processes. We have also found that a lower tincontent of the feedstock, brings the advantage that the solubility ofcopper in the feedstock is reduced, which leads to a lower coppercontent in the ultimate prime products, such as tin and lead, afterfurther downstream processing by for example vacuum distillation, whichincreases the economic value of these prime products and/or reduces theburden of removing the remaining traces of copper in a furtherdownstream copper removing process step.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,more than 1.00% wt of copper, preferably at least 1.02% wt, morepreferably at least 1.05% wt, preferably at least 1.07% wt, morepreferably at least 1.10% wt, even more preferably at least 1.12% wt,yet more preferably at least 1.15% wt of copper, preferably at least1.17% wt, more preferably at least 1.19% wt, even more preferably atleast 1.20% wt, preferably at least 1.30% wt, more preferably at least1.40% wt, even more preferably at least 1.60% wt, more preferably atleast 1.80% wt, even more preferably at least 1.90% wt of copper.

We have found that the amounts of copper, as specified in accordancewith the present invention, may be left in the crude solder withoutdestroying the usefulness of the solder after tuning as furtherfeedstock for a vacuum distillation step, hence without significantlyreducing or destroying the effect which is obtained by the presentinvention, i.e. increasing the risk that a vacuum distillation stepperformed on the tuned solder, would not anymore be able to operate incontinuous mode over an extended period of time without encounteringproblems of intermetallic compounds comprising copper which impair thedistillation operations. We have found that the identified problems maybe reduced to a practically and economically acceptable level when thesmall amounts of copper, as specified, remain present in the crudesolder according to the present invention, when used after tuning as thefeedstock for a vacuum distillation step to separate off at least a partof the lead in the solder stream.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,less than 10% wt of copper, preferably at most 9% wt, more preferably atmost 8% wt, preferably at most 7% wt, more preferably at most 6% wt, andyet more preferably at most 5.7% wt, preferably at most 5.5% wt, morepreferably at most 5% wt, even more preferably at most 4.5% wt,preferably at most 4% wt, more preferably at most 3.5% wt, preferably atmost 3% wt, more preferably at most 2.5% wt, even more preferably atmost 2% wt of copper.

We have found that the lower the concentration of copper in thefeedstock, the lower the risk for the formation of intermetalliccompounds when the crude solder obtainable by the process according tothe present invention, after tuning is subjected to vacuum distillation.We have further found that the lower the copper presence in thefeedstock, the lower the concentration of copper in the product streamsfrom the downstream vacuum distillation. This reduces the burden in thefurther removal of copper from these streams on their path towardsbecoming prime products, in particular in terms of chemicals consumptionand in terms of amounts of by-products formed.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,more than 0.02% wt of antimony, preferably at least 0.05% wt, morepreferably at least 0.08% wt, preferably at least 0.10% wt, morepreferably at least 0.12% wt, even more preferably at least 0.14% wt,yet more preferably at least 0.16% wt of antimony, preferably at least0.18% wt, more preferably at least 0.20% wt, even more preferably atleast 0.22% wt, preferably at least 0.24% wt, more preferably at least0.26% wt, even more preferably at least 0.28% wt, preferably at least0.30% wt, more preferably at least 0.32% wt, even more preferably atleast 0.34% wt, yet more preferably at least 0.36% wt of antimony.

We have found that the feedstock may contain measurable, and evensignificant, amounts of antimony, within the specified limits, withoutthis presence of antimony bringing significant impairment to possibledownstream vacuum distillation. We have found that this provides extrafreedom of operation for the feedstock. Thanks to this allowance of anamount of antimony in the crude solder obtainable by the processaccording to the present invention, the process according to the presentinvention is capable of accepting a feedstock in which antimony ispresent. Antimony may be present in a variety of primary and secondaryfeedstocks for non-ferrous metals, as well as in many end-of-lifematerials. Antimony may for instance be present in lead which was usedsince Roman times for plumbing. These materials may now become availableas demolition materials, often in combination with copper for tubing andother purposes, and with tin and lead for the solder connections.Allowing an amount of antimony in the crude solder obtainable by theprocess according to the present invention, provides the processaccording to the present invention to accept such mixed end-of-lifematerials in the feedstock. We have found that significantconcentrations of antimony are allowed in the crude solder obtainable bythe process according to the present invention without this creatingsignificant difficulties for the downstream processes.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,less than 5% wt of antimony, preferably at most 4% wt, more preferablyat most 3% wt, even more preferably at most 2% wt, yet more preferablyat most 1.5% wt, preferably at most 1.00 wt % of antimony, morepreferably at most 0.95% wt, even more preferably at most 0.9% wt,preferably at most 0.87% wt, more preferably at most 0.85% wt, even morepreferably at most 0.8% wt, yet more preferably at most 0.75% wt,preferably at most 0.7% wt, more preferably at most 0.65% wt, even morepreferably at most 0.6% wt, preferably at most 0.5% wt, more preferablyat most 0.4% wt, even more preferably at most 0.35% wt of antimony.

We have found that antimony may be allowed in the feedstock, withinspecific limits, without creating problems when the crude solderobtainable by the process according to the present invention is tunedand used as feedstock for downstream vacuum distillation. We have foundthat it is important to keep the amount of antimony below the specifiedupper limit because antimony may also at least partially evaporate underthe distillation conditions. If the level of antimony is higher, theamount of antimony leaving the distillation step with the high leadcontaining overhead product may become significant. In order to obtainthe higher purity prime lead product complying with the desired industrystandards, this amount of antimony needs to be removed from this leadstream in the conventional clean-up steps downstream of the distillationstep. An amount of antimony above the specified limit increases theburden of these downstream clean-up steps and increases the amount ofby-product streams containing the antimony. Because these by-productstreams may also contain significant amounts of lead, this lead in theby-products is not ending up in the prime lead product and at leastreduces the effectiveness of the overall operation.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,more than 0.0004% wt of bismuth, preferably at least 0.0005% wt, morepreferably at least 0.0006% wt, preferably at least 0.0007% wt, morepreferably at least 0.0008% wt, even more preferably at least 0.0009%wt, yet even more preferably at least 0.0010% wt of bismuth, preferablyat least 0.002% wt, preferably at least 0.003% wt, more preferably atleast 0.004% wt, even more preferably at least 0.005% wt, preferably atleast 0.0075% wt, more preferably at least 0.01% wt, even morepreferably at least 0.0125% wt, yet even more preferably at least 0.015%wt, preferably at least 0.020% wt of bismuth.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,less than 1.0% wt of bismuth, preferably at most 0.8% wt, preferably atmost 0.6% wt, more preferably at most 0.4% wt, even more preferably atmost 0.2% wt, and yet even more preferably at most 0.1% wt of bismuth,preferably at most 0.08% wt, more preferably at most 0.06% wt, even morepreferably at most 0.05% wt, preferably at most 0.04% wt, morepreferably at most 0.03% wt, even more preferably at most 0.025% wt ofbismuth.

We have found that bismuth may be allowed in the feedstock, withinspecific limits. We have found that bismuth may be relatively volatileunder the conditions of the vacuum distillation step. Some of thebismuth may therefore find its way into the prime products, from whichit may then need to be removed in order to obtain a prime product thatcomplies with the desired product specifications. This downstreamcontaminant removal consumes chemicals and creates a by-product streamwhich contains also some valuable prime product. Even if successfullyrecycled, these by-product streams represent a process inefficiencywhich is advantageously reduced. Therefore it is more advantageous tolimit the amount of bismuth in the feedstock.

We have further found that the risk for the formation of potentiallydisturbing intermetallic compounds is reduced by controlling thepresence of the above mentioned compounds, tin, copper, antimony andbismuth, in the feedstock between the mentioned levels.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,less than 1.0 wt % of arsenic, preferably at most 0.8% wt, morepreferably at most 0.6% wt, preferably at most 0.4% wt, more preferablyat most 0.3% wt, even more preferably at most 0.20% wt, and yet evenmore preferably at most 0.185% wt of arsenic, preferably at most 0.18%wt, more preferably at most 0.175% wt, even more preferably at most0.170% wt, preferably at most 0.15% wt, more preferably at most 0.13%wt, even more preferably at most 0.11% wt of arsenic.

We prefer to keep the amounts of arsenic in the feedstock within limits.This reduces the burden of removing arsenic downstream from any of theproduct streams from a possible vacuum distillation step. Thesedownstream removal steps use chemicals and generate by-product streamswhich inevitably contain also some amounts of valuable metals such aslead and/or tin. Even if successfully recycled, these by-product streamsrepresent an overall process inefficiency, and it is advantageous toreduce their volume. Recycling may also bring problems caused by thechemicals in these by-product streams, such as a corrosive effect onrefractory materials used in the equipment and in contact with the hotliquid streams.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstockless than 2.0 wt % of nickel, preferably at most 1.7% wt, morepreferably at most 1.5% wt, even more preferably at most 1.2% wt, yeteven more preferably at most 1.0% wt, preferably at most 0.8% wt, morepreferably at most 0.6% wt, preferably at most 0.50% wt, more preferablyat most 0.45% wt, even more preferably at most 0.40% wt, and yet morepreferably at most 0.35% wt of nickel, preferably at most 0.30% wt, morepreferably at most 0.29% wt, even more preferably at most 0.28% wt,preferably at most 0.26% wt, more preferably at most 0.24% wt, even morepreferably at most 0.22% wt, preferably at most 0.20% wt, morepreferably at most 0.18% wt, even more preferably at most 0.16% wt,preferably at most 0.14% wt, more preferably at most 0.12% wt of nickel.

We have found that the risk for the formation of potentially disturbingintermetallic compounds is reduced by controlling the presence of theabove mentioned compounds, arsenic and nickel, in the feedstock belowlower levels. Nickel is a metal which is present in many raw materialsavailable for the recovery of non-ferrous metals, in particular insecondary raw materials, and especially in end-of-life materials. It isthus important in the recovery of non-ferrous metals that the process iscapable of coping with the presence of nickel. Furthermore, thepyrometallurgical processes for recovering non-ferrous metals oftenconsume significant amounts of iron as a process chemical. It isadvantageous to be able to use secondary iron-containing materials forthis purpose. These materials may, besides high amounts of iron, alsocontain minor amounts of nickel. It is advantageous to be able to alsocope with a certain amount of these kinds of process chemicals. We havefurther found that it is preferred to bring down the nickel content inthe feedstock to the process according to the present invention, ratherthan removing larger amounts of nickel downstream. Such downstreamnickel removal is typically performed together with removing arsenic(As) and/or antimony (Sb), and carry a risk for generating the verytoxic gasses arsine (AsH₃) and/or stibine (SbH₃). The nickel removaldown to within the specified limits therefore also reduces thedownstream risk for the generation of toxic gasses, and is thus also asafety and industrial hygiene measure.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstock,at least 8% wt of lead, preferably at least 10% wt, more preferably atleast 15% wt, even more preferably at least 20% wt, preferably at least22% wt, more preferably at least 24% wt, even more preferably at least26% wt, yet more preferably at least 30% wt of lead, preferably at least33% wt, more preferably at least 36% wt, even more preferably at least40% wt of lead.

In an embodiment of the process according to the present invention, thefeedstock comprises, relative to the total dry weight of the feedstockat most 80% wt of lead, preferably less than 79% wt, more preferably atmost 75% wt, even more preferably at most 70% wt, yet more preferably atmost 69% wt, and yet even more preferably at most 68% wt of lead,preferably at most 65% wt, more preferably at most 60% wt, preferably atmost 55% wt, more preferably at most 50% wt, even more preferably atmost 45% wt, preferably at most 42% wt, more preferably at most 41% wt,preferably at most 40% wt, more preferably at most 35% wt, even morepreferably at most 30% wt of lead. The applicants prefer to operate withthe lead content within the prescribed limits, because on the one handit offers the advantage of a high density solder which facilitatesseparation by gravity of the molten solder from the slag phase, and onthe other hand it leaves significant room for tin metal, which issubstantially more valuable than lead, which is beneficial for theeconomic value added of the process according to the present invention.

In an embodiment of the process according to the present invention, thefeedstock is characterized by a lead/tin (Pb/Sn) weight ratio of morethan 0.50, preferably at least 0.52, more preferably at least 0.53,preferably at least 0.54, more preferably at least 0.55, even morepreferably at least 0.56, yet more preferably at least 0.57, preferablyat least 0.60, more preferably at least 0.65, even more preferably atleast 0.70, preferably at least 0.80, more preferably at least 0.90.

In an embodiment of the process according to the present invention, thefeedstock is characterized by a lead/tin ratio which is less than 4.0,preferably at most 3.5, more preferably at most 3.2, even morepreferably at most 3.1, preferably at most 3.0, more preferably at most2.9, and yet more preferably at most 2.8, preferably at most 2.5, morepreferably at most 2.2, even more preferably at most 2.0, preferably atmost 1.8, more preferably at most 1.6.

The inventors have found that the remaining slag comprises lower amountsof valuable tin when the lead/tin ratio is between the mentioned levels.When the lead/tin ratio of the feedstock is too low, i.e. below 0.5,more lead containing materials are preferably added to the feedstockuntil a ratio of at least 0.5 is obtained. The inventors have found,when the feedstock comprises more lead, that the relative amount of tinin the crude solder relative to the amount of tin in the feedstock, isalso higher. The inventors have found, by offering more lead togetherwith the tin, that the recovery of tin in the process is improved, andless of the available tin is ending up in the slag. The inventors havefound that having the lead/tin ratio within the prescribed limitsimproves the various separation steps in the overall process thatoperate on the basis of gravity.

As detailed above, the process according to the present inventioncomprises the step a) and/or step j) of building a liquid bath of ametal phase and/or a slag in a furnace by heating and melting at least apart of the feedstock which feedstock is preferably retained by a sievewith a sieve opening equal to or smaller than 3.0 mm.

In an embodiment of the process according to the present invention, stepa) and/or step j) further comprises the addition of lead into thefurnace, preferably in the form of lead metal, lead scrap or leadcompounds, preferably lead oxides.

The inventors have found that the addition of lead dilutes the Sn inboth the metal phase as well as in the slag, whereby the recovery of theSn, available in the furnace, into crude solder is improved. Theinventors have further found that the downstream processing of the crudesolder is improved by a higher Pb presence.

The furnace as used in step a) and/or step j) of the process accordingto the present invention may be any furnace known in the art ofpyrometallurgy such as an Isasmelt furnace, an Ausmelt furnace, atop-blown rotary converter (TBRC) or a smelter.

In an embodiment, the furnace as used in step a) and/or step j) of theprocess according to the present invention, is a smelter.

In a smelting furnace the metals are molten, and organics and othercombustible materials are burned off. The smelter is therefore able toaccommodate much more low quality raw materials, which are usually moreabundantly available at economically more attractive conditions.

The process according to the present invention, performed in a smelter,may thus accept raw materials that alternate processes known in the artmay not accept, or only accept in very limited quantities, and which maythus be more readily available at economically more attractiveconditions.

The applicants have found that a smelter step is highly suitable, andeven preferable, for performing the process according to the presentinvention. A smelter step offers the advantage of being simple inoperation and in equipment, hence economically advantageous. A smelterstep brings the further advantage of being tolerant in terms of rawmaterial quality. A smelter step is able to accept raw materials thatare highly diluted and/or contaminated with a wide variety ofcomponents, including organic materials, rubbers, plastics, paint, wood,and the like. Because these mixed and/or contaminated raw materials havehardly any other end-use, they may be supplied at economically veryattractive conditions. The capability of processing these raw materialsand upgrading the valuable metals contained therein, is therefore ofinterest to the operator of the process according to the presentinvention.

The inventors have found that the process according to the presentinvention is preferably carried out in a smelter because the processaccording to the present invention is then capable of easily acceptingfeedstocks in finely divided form without any operational problems. Afurther advantage of using a smelter is that a smelter is a fairlysimple and inexpensive apparatus, typically consisting of a largecylinder-shaped furnace which only needs to be able to tilt around itsaxis over a part of a full circle.

In an embodiment of the process according to the present invention, thepart or portion of the feedstock used in step a) and/or step j)comprises divided solid material and comprises at most 5% wt ofparticles which pass through a sieve having a sieve opening of 2.0 mm,also known as a Mesh 9 sieve, preferably less than 5% wt, morepreferably at most 4% wt, even more preferably at most 3% wt, yet morepreferably at most 2% wt and yet even more preferably at most 1.0% wt.

In an embodiment of the process according to the present invention, thepart of the feedstock used in step a) and/or step j) comprises at most5% wt of particles which pass through a sieve having a sieve opening of2.38 mm, also known as a Mesh 8 sieve, preferably a sieve opening of2.83 mm, also known as a Mesh 7 sieve, more preferably a sieve openingof 3.36 mm, also known as a Mesh 6 sieve, and preferably less than 5%wt, more preferably at most 4% wt, even more preferably at most 3% wt,yet more preferably at most 2% wt and yet even more preferably at most1% wt.

We have observed that many of the secondary feedstocks for non-ferrousmetal recovery are primarily available in a finely divided form, orcontain significant portions of small particles.

The inventors have found that it is advantageous to restrict the part ofthe feedstock which is used in step a) and/or step j) in terms of itscontent of finely divided material. This may for instance be achieved bysieving at least a portion of the feedstock before this is used in stepa) and/or step j), and only using the part that is retained by the sieveas specified. Another suitable possibility is to keep the raw materialsthat are rich in finely divided material separate from raw materialsthat have low or no finely divided material content, and use only thelatter for introduction into step a) and/or step j) of the processaccording to the present invention.

The advantage of this feature is that thereby the risk is reduced thatmany of the small particles in the feed would be blown out of thefurnace in which the liquid bath of molten metal is built as part ofstep a) and/or step j), and therefore would not end up as part of theliquid bath. In particular when the feedstock is heated and/or melted bythe combustion of a liquid or gaseous fuel with air and/or oxygen, thestep a) and/or step j) may be characterised by a large volume of exhaustgasses, and the gas velocities inside the furnace and in the flue gasexhaust duct may be high. Gas at high velocity is able to readily carryalong small solid particles, and the smaller the easier these arecarried along. Solid particles being entrained with the furnace exhaustgasses do not anymore participate in the process step. They create anextra burden on the exhaust gas treatment equipment, because they needto be removed before the exhaust gasses may be released to theatmosphere. When recovered, these solid particles or dust preferablyneed to be reprocessed, rather than being disposed of as waste.

The inventors have found that by increasing the mesh size or sieveopenings of the sieves which are to retain the feedstock for step a)and/or step j), brings the benefit that step a) and/or step j) may beoperated with higher gas velocities without increasing the risk for dustentrainment from the furnace into the exhaust gasses. Higher gasvelocities means that the energy input into the furnace may beincreased, and that the building of the liquid bath in step a) and/orstep j) may be less time consuming.

In an embodiment of the process according to the present invention, thepieces used as the feedstock have at least two dimensions that aresmaller than 0.5 m. This brings the advantage that all the pieces mayreadily pass a typical feeding opening of a furnace for operating theprocess of the present invention, which is a square of 0.5×0.5 m size.

The inventors have found that using a feedstock which is retained by asieve with a prescribed sieve opening, also avoids possible industrialhygiene issues associated with feedstock dust in the working environmentand atmosphere.

Many of the feedstocks comprising valuable Sn and/or Pb are available ina finely divided form. For example, exhaust dust collected in off-gasdust filter units or the output of drying units where the oxidic metalraw materials are mixed, dried and sieved, often contain significantamounts of Sn and/or Pb. The finely divided feedstocks are preferablynot fed into step a) and/or step j) of the process according to thepresent invention, because of the reasons mentioned above. The inventorshave however found that the process according to the present inventionis capable of accepting finely divided feedstocks without operationalproblems, such as when the finely divided feedstocks are injected intothe liquid bath which is present in the furnace during operation,preferably when a suitably and sufficiently large amount of liquid bathis present, more preferably the liquid bath comprising a layer of liquidslag, such as when a liquid bath has been built from the larger sizefeedstock material that is preferred for step a) and/or step j).

In a further embodiment, the process according to the present inventionfurther comprises the step of injecting, into the liquid bath that hasbeen formed in step a) and/or step j), a finely divided portion of thefeedstock, the finely divided feedstock portion having an averageparticle size of at most 10 mm, preferably at most 8 mm, more preferablyat most 6 mm, even more preferably at most 5 mm, yet more preferably atmost 4 mm, preferably at most 3 mm, more preferably an average particlesize that is smaller than the sieve opening prescribed in thecharacterization of the portion of the preferred feedstock for step a)and/or step j). The finely divided feedstock portion may be injectedinto the molten metal phase, if present, and/or into the molten metaloxide slag phase, if present. Preferred is to inject the finely dividedfeedstock portion below the liquid level of the liquid bath formed inthe furnace after step a) and/or step j), such that the risk forentrainment of the small particles with the exhaust gas stream from thefurnace is reduced. This brings the advantage that the process iscapable of coping with feedstock materials that are available in afinely divided form. There are many sources of suitable finely dividedfeedstock materials. Because these are less acceptable in alternativeapplications, the capability of the process to cope with these feedstockmaterials represents a higher economic upgrade.

In an embodiment, the finely divided feedstock portion is injected intothe liquid slag phase and above the metal phase of the liquid bath. Thisbrings the advantage that the material is readily incorporated into theliquid bath, quickly melts and reacts to form the desired reduced metaland oxidized metal components, which may then readily find their waysinto the respective liquid phases according to their densities. Thisfeature brings the extra advantage that the injection of the finelydivided feedstock portion brings only a low extra disturbance of theformation of the two phases in the liquid bath, i.e. the lower phase ofmolten metal and the upper phase of liquid slag.

The inventors have found that injecting the finely divided feedstockportion or material into the liquid slag phase increases the absorptionof the finely divided feedstock particles into the slag by increasingthe residence time thereof in the liquid phase. The inventors havefurther found that preferably a suitably and sufficiently large amountof slag is made to be present before the finely divided feedstock isinjected. The applicants prefer to inject the finely divided feedstockportion or material into the bath only when a continuous supernatantslag phase is present in the liquid bath. This brings the advantage thatthe risk is strongly reduced that a significant part of the finelydivided feedstock portion would not be retained in the liquid bath, andleave the furnace with the exhaust gasses. Typically, a suitable amountof slag phase for a convenient injection of finely divided feedstockmaterial is 0.6 ton, preferably 0.65 ton, more preferably 0.7 ton, perton of metal in the liquid bath.

In an embodiment of the process according to the present invention, thefinely divided feedstock portion material has an average particle sizeof at most 3.36 mm, preferably at most 2.83 mm, more preferably at most2.38 mm, even more preferably at most 2.00 mm, yet even more preferablyat most 1.68 mm, preferably at most 1.50 mm, more preferably at most1.30 mm, even more preferably at most 1.20 mm, yet more preferably atmost 1.10 mm, yet even more preferably at most 1.00 mm. The applicantshave found that the smaller the finely divided feedstock particles, thefewer the possible alternative dispositions for this material, and hencethe higher the possible upgrade that may be brought by the processaccording to the present invention. The applicants have further foundthat the smaller the finely divided feedstock particles the morereactive these particles are, and the faster the same amount offeedstock may be processed in the process according to the presentinvention.

The injection of the finely divided feedstock portion may be performedby suitable injection techniques known to those skilled in the art, forexample by injection with the aid of pressurized air.

In an embodiment, the liquid bath of molten metal that is obtained instep a) and/or step j) of the process according to the present inventionis kept at a temperature of at least 975° C., preferably at least 1000°C., more preferably at least 1050° C., even more preferably at least1075° C., yet even more preferably at least 1100° C., more preferably atleast 1125° C., even more preferably at least 1150° C. The applicantshave found that this lower limit as specified brings the advantage thatthe slag in the furnace remains fluid and with a viscosity that readilyallows the pouring of the slag from the furnace without significantentrainment of portions of the underlying molten metal phase.

In an embodiment, the liquid bath of molten metal that is obtained instep a) and/or step j) of the process according to the present inventionis kept at a temperature of at most 1360° C., preferably at most 1340°C., more preferably at most 1320° C., even more preferably at most 1300°C., yet more preferably at most 1280° C., preferably at most 1240° C.,even more preferably at most 1220° C. The applicants have found that theupper limit as specified brings the advantage of reduced wear and/ordamage to the furnace equipment that is in contact with the hot liquidbath.

As detailed above, the process according to the present inventioncomprises the step b) and/or step k) in which at least one reducingagent is introduced into the liquid bath to reduce at least a part ofthe oxidized valence form of tin and/or lead into tin and/or lead metalrespectively. As stated elsewhere, the oxidized valence form of tinand/or lead is preferably tin and/or lead oxide.

In a preferred embodiment, the at least one reducing agent is a metallicmaterial comprising at most 25% wt of copper.

Preferred reducing agents for step b) and/or step k) are lowCu-containing metallic materials. In the context of the presentinvention, the term “low Cu-containing metallic materials” meansmetallic materials that are containing less than 25% wt of copper,preferably Sn and SnZn metallic materials containing less than 25% wt ofcopper.

The term “metallic materials” means materials of which the total metalcontent, relative to the total dry weight of the material, is prescribedin an identical manner as the total metal content of the feedstock ofthe process according to the present invention.

The reducing agent used in step b) and/or step k) of the processaccording to the present invention is added to reduce possible Sn and/orPb oxides into their metals and is typically selected from carbon,metals less noble than Sn and Pb, and secondary feedstocks rich inelemental Fe, Al and/or Si, preferably secondary feedstocks rich in Fe,Al and/or Si metal. Typically any silicon metal present in the preferredreducing agent is secondary in amount or incidental, because materialsrich in silicon metal are rather scarce and may readily find analternative and higher value disposition as compared to its use as areducing agent in the process according to the present invention.

We have found, with feedstocks containing oxidised metal components suchas Cu, Sn, Pb and/or Ni oxides, that many of these metal oxidecomponents may readily be reduced to liberate their respective freemetal forms by introducing into the furnace other, and preferablysecondary, feedstocks that are rich in elemental Fe, Al and/or Si, suchas ferrosilicon (FeSi). Such Fe, Al and/or Si metals are allowed to becontaminated with additional Cu or Sn, and may thus be streams having alimited number of disposal options, such as some of the waste streamsfrom silicon manufacturing for electronic end-uses. The Fe, Al and/or Simetal is able to react with the oxides of the more noble elements Cu,Sn, Pb, Ni. As a result of this reaction, the less noble metals Fe, Al,Si will be oxidised, their oxides will have a tendency to become part ofthe slag, and be readily separable from the bath of reduced metals.

We have further found that the added reducing agent, which is usuallysolid, typically floats at the interface between the liquid metal phaseand the slag, exactly in the reaction zone where it may performoptimally as a reducing agent. These oxidation/reduction reactions maygenerate sufficient heat to melt the additional feed and to maintain thetemperature in the furnace. The inventors have found that elemental Aland Si provide significantly more energy than Fe, but in excessivelyhigh concentrations Al and Si may increase the viscosity of the slag.The inventors have further found that the total amount and the overallcomposition of the added reducing agent is preferably adjusted incorrespondence to the amount of target metals present in the bath in theform of their oxides and which should be reduced, and also preferablythat the addition is performed gradually and/or intermittently, in sucha way that the reaction continues in a controlled way in order tomaintain a steady operation.

In one embodiment of the process according to the present invention, theat least one reducing agent comprises secondary feedstocks rich in Fe,such as containing at least 20% wt of Fe, preferably at least 30% wt Fe,more preferably at least 40% wt Fe, even more preferably at least 45% wtFe. Preferably these secondary feedstocks are not only rich in Fe butfurther contain some Sn, such as at least 3% Sn, preferably at least 5%wt of Sn, more preferably at least 10% wt Sn, and in addition are fairlylow in Cu, such as at most 5% wt Cu, preferably at most 3% wt Cu, evenmore preferably at most 1.5% wt of Cu. Suitable reducing agents in thiscategory may for instance be FeSn granulates, available in variouspurity grades, and which are often referred to as “hardhead”, a termwhich is quite commonly used in the metallurgical field.

Conventionally, carbon has often been used as the reducing agent.However, the inventors have found that carbon may form a foamy slagwhich may cause the furnace to overflow. In addition, the CO₂ which isgenerated in the reduction reaction, and which is escaping as a hot gasfrom the furnace, represents a significant heat loss. The inventors havefurther found that in the process according to the present invention,the reduction reaction of Sn and/or Pb from their oxides into metals, asa result of the addition of a reducing agent in step b) and/or step k),may at least partly be achieved by the introduction of secondaryfeedstocks rich in Fe, preferably containing some Sn, while being low inCu, without the formation of a foamy slag or representing a loss ofheat. The oxides of the more noble metals in the slag, such as Sn andPb, are reduced by addition of Fe metal, whereby the Fe metal convertsinto an oxidized form which moves up into the supernatant slag, and themore noble metals such as Sn and Pb end up into the heavier metal phaseunderneath. The inventors have further found, to improve the kinetics ofthe reaction, that the Fe metal feed preferably has a large specificsurface. Therefore, fine sheets of scrap metal are preferably used, forinstance Fe/Sn waste material such as production waste from the metalcan industry. Reject materials from the metal can industry and/or frommetal cans after their useful life have little to no other usefuldisposition and represent a concern for their disposal as landfill.

In an embodiment, the at least one reducing agent comprisesmetal-containing sand, such as “foundry sand”.

The inventors have found that such metal-containing sand or foundry sandis quite suitable as a reducing agent in step b) and/or step k) of theprocess according to the present invention. Foundry sand is a wastestream of foundries. Clean sand, usually treated with a small amount oforganic binder, is used to form a mould, in which then the red-hot andliquid iron or steel is cast. The organic binder substantially burnsaway during the casting. After cooling, the sand is fairly free-flowingand the cast metal object is readily recovered by removing the sand.Only a part of this sand may be reused because it has become too heavilycontaminated with metal during the production process. A significantpart therefore has to be discarded. This contaminated sand is calledfoundry sand. Foundry sand has little to no other useful or valuabledisposition and therefore is often landfilled. The discard as landfillrepresents an environmental burden which is becoming increasinglyproblematic for the foundry operator. We have found that the foundrysand is an interesting reducing agent in step b) and/or step k) of theprocess according to the present invention, because of its readyavailability from a high number of sources and the lack of high valuealternative disposal options.

As detailed above, the process according to the present inventioncomprises the optional step c) and/or step l) in which is introducedinto the furnace at least one energy source comprising at least onemetal being less noble than Sn and Pb, and wherein the at least onemetal in the energy source is oxidized by the injection of air and/oroxygen into the furnace.

In an embodiment, step c) and/or step l) is present in the processaccording to the present invention.

The energy source as used in step c) and/or step I) of the processaccording to the present invention is preferably selected from the groupconsisting of metals which are less noble than Sn and Pb, in particularselected from elemental Fe, Si, Mg, Zn, Al, Ca and Na, alternativelyalso called the respective “metal”, and combinations thereof.

In an embodiment of the process according to the present inventionwherein step c) and/or step l) is present, air and/or oxygen is injectedinto the liquid bath, typically in the form of enriched air, morepreferably as purified oxygen gas.

We have found that a metal less noble than Sn and Pb is able to deliverextra energy by liberating the heat of oxidation while simultaneouslyreducing Sn and/or Pb oxides to their elemental metal forms. Inaddition, extra energy may be generated by the injection of a suitableform of oxygen gas into the liquid bath.

The inventors have found that the oxygen gas is preferably injectedbelow the liquid level in the furnace, i.e. directly into the liquidbath. This brings the advantage of a lower risk for losing part of theoxygen in the exhaust gasses, and thus improves the effectiveness of theoxygen gas injection, hence improves the energy efficiency of theprocess.

The inventors have further found that an oxygen gas injection,optionally in combination or in mixture with natural gas, provides anindependent and convenient way for controlling and independentlyadjusting the total energy input into the furnace by controlling theflow of oxygen. Without the input of oxygen, pure or diluted, all theenergy input would have to be delivered by the oxidation of metals addedto the furnace. The energy input rate would then not be readilycontrollable, which represents a risk for temperature runaways. Themaintenance of an oxygen gas injection for satisfying part of the energyrequirements into the furnace therefore improves the controllability ofthe energy input rate into the furnace, and reduces the risk foruncontrollable temperature excursions with possibly disastrousconsequences.

As detailed above, the process according to the present inventioncomprises the step d) and/or step m) in which the crude solder isseparated from the slag.

It is understood that the separation may be obtained by any suitablemethod known to the skilled person in the art.

In an embodiment of the process according to the present invention, instep d) and/or step m) the removal from the furnace of the crude solderand/or the slag is performed by tapping the crude solder and/or the slagas a liquid from the furnace.

The inventors have found that when the furnace is a smelter furnace, thecrude solder may be tapped during and/or at the end of the batch orcampaign by tilting the smelter into one direction, whereby the crudesolder is allowed to flow through a tap hole in the smelter wall into asuitable container.

In an embodiment of the process according to the present invention,wherein in step d) and/or step m) the crude solder is tapped as a liquidfrom the furnace, the process further comprises the step ofcooling/solidifying the tapped crude solder by contacting the crudesolder with water to obtain crude solder granulates.

The applicants have found that the crude solder in the form ofgranulates is easier to handle and to transport over long distances,such as when the crude solder is upgraded in a separate apparatus thatmay be located at a long distance from the point of production.

The inventors have further found, when the furnace is a smelter furnace,that at the end of a production batch the slag may be poured into a panthrough the charge opening of the smelter, by tilting the smeltersideways, and subsequently be cooled/solidified in direct contact withwater, typically thereby forming granules or a granulate product. Thedirect contact with water ensures a quick quenching which causes thesolder to end up as solder granulates which are easy to handle. We havefound that quick quenching is more advantageous compared to slowsolidification because it is much faster, requires less plot space andthe product is easier to handle. We have further found that it isadvantageous to use an amount of water which is sufficient to transportthe slag granulates to the granulation pit for settling, and to at leastpartially recycle the water. The solder granulates may then be removedfrom the granulation pit by means of a crane or scoop. The soldergranulates may be sold or upgraded.

In an embodiment, the process according to the present invention furthercomprises the step of recovering metal values from the slag from step d)and/or step m). The applicants have found that the slag from step d)and/or step m) contains sufficient amounts of tin and/or lead, andusually also of other valuable metals, such as copper or zinc, tojustify the recovery thereof. The slag is also too rich in leachablemetals, such that a disposal of landfill of the slag would entailcomplex precautions in order to avoid possible pollution problems ofsoil and/or ground water. The recovery of metal values from the slag maybe achieved by introducing the slag from step d) and/or step m) in apyrometallurgical process for the production of a non-ferrous metal,such as copper, zinc or nickel, preferably recovering the tin and/or thelead in the slag into a by-product from the non-ferrous metalproduction, which by-product may be returned into the process accordingto the present invention, in step a) or downstream thereof.

The slag from step d) and/or step m) may for instance be recycled duringa copper production campaign, preferably in the same furnace,particularly when the slag granulates contain significant amounts ofuseful metals such as Pb and Sn.

In an embodiment, step d) and/or step m) of the process according to thepresent invention further comprises, prior to the separation of the slagfrom the crude solder and to the removal of at least a portion of theslag in step d) and/or step m), the addition to the furnace of an amountof inert solid particulate material, preferably sand (primarilyconsisting of SiO₂) or spent slag on top of the slag, typically as ashielding material.

The inventors have found that the amount of inert solid particulatematerial, typically sand or spent slag, should be chosen such that it issufficient for building a solid layer on top of the liquid level at theexit mouth of the furnace, i.e. sufficient to act as a shieldingmaterial. The inert solid particulate material is preferably spread ontop of the liquid level. The inert solid material is also preferablyadded only shortly before the slag is removed from the furnace by“pouring” the slag phase. This brings the advantage that less of thesolid material has the time and the temperature exposure necessary tomelt and to move into the liquid bath, so that more of the solidmaterial remains available for forming the “shield”, when the slag ispoured, which retains other solid material that may be floating on topof the liquid bath. Readily acceptable particulate materials arematerials that do not disturb the slag/metal equilibrium, norsignificantly affect the flow characteristics of the slag phase. Mostpreferably the particulate materials are readily available in abundanceand at low cost. Clean sand is quite suitable, and so is a granulatedform of a final slag with high melting point, such as a final slag fromcopper refining. The inventors have further found that the shieldingmaterial may form a shell in the furnace mouth which prevents theoverflow of solid, unmolten pieces which may be floating on the liquidinside the furnace. Furthermore, sand is a convenient and readilyavailable source of silicon dioxide in suitable purity for achieving thedesired result without impairing the process in any way. The silicondioxide ending up in the slag may readily be recycled to an upstreamsmelting step, where the silicon dioxide typically ends up in the finalspent slag by-product from the smelter, and in which it may bringfurther benefits. By preference the inert solid particulate material isdistributed over a large area of the bath surface, such that it reachesa large portion of the slag floating on top of the crude solder in theliquid bath.

We prefer that the shielding material is in a finely divided form, suchas a powder or granulates. The applicants have found that a finelydivided form more readily distributes over the surface of the liquidbath.

In an embodiment, step d) and/or step m) of the process according to thepresent invention further comprises, prior to the separation of the slagand the crude solder, the addition of a flux material comprising SiO₂.

A highly suitable flux material containing SiO₂ is sand, because it ishighly rich in SiO₂ and sources of sand that is lean in potentiallydisturbing other compounds may readily be found. The applicants havehowever found that suitable alternatives exist, some of which beingavailable at economically even more attractive conditions. The processaccording to the present invention is capable of handling flux materialthat contains, apart from SiO₂, particular metals, such as Sn, Pb, Cu,Fe, Ni, and/or oxides thereof. These metals, even when introduced as theoxides, may be recovered as part of the overall process, and hence mayat least partially be upgraded. The applicants have for instance foundthat lead glass (“crystal glass”) or the waste form thereof, is a verysuitable flux material for step d) and/or step m), while this type ofwaste streams has difficulties finding alternative economic uses. Theapplicants have found that the cathode-ray-tubes (CRTs) used in oldergeneration television sets, monitors for computers and other electronicequipment, or radar targets, are quite acceptable as a source forsuitable flux material, and advantageous because the face of the CRT istypically made up by thick and heavy lead glass, in particular when itwas used as part of a consumer product.

The inventors have found that the addition of a flux material causes areduction in the melting temperature of the slag and/or a reduction ofthe slag viscosity (and thus increase in fluidity) at a particulartemperature. We have found, as an additional benefit, that significantamounts of SiO₂ also reduce the SnO₂ content of the slag by acidifyingthe slag and thereby pushing SnO₂ out of the slag by affecting theactivity of SnO₂, which oxide readily reduces to Sn and thus moves intothe metal phase.

We have further found that adding SiO₂ to the furnace in step d) and/orstep m) converts FeO in the slag into FeO—SiO₂, according to thefollowing reaction

2FeO+SiO₂->(FeO)₂.SiO₂.

Preferably sufficient conversion of FeO into (FeO)₂—SiO₂ is obtained inorder to reduce and preferably eliminate the risk for explosions whenthe slag is removed from the furnace and granulated in contact withwater. Under the typical process conditions of slag granulation, FeO isable to act as a catalyst for the decomposition of water into hydrogenand oxygen, whereas (FeO)₂.SiO₂ is inactive for that reaction. Thestoichiometric amount of SiO₂ necessary to convert all FeO is 1 mole ofSiO₂ for every 2 moles of FeO, hence 0.42 grams of SiO₂ for every 1 gramof FeO. The applicants therefore prefer to use a weight ratio FeO/SiO2of about 2.4.

In an embodiment, the process according to the present inventioncomprises at least one of a number of further steps in which the crudesolder obtained from step d) and/or step m) is further treated or“tuned” to become a tuned solder that is suitable as a feedstock forvacuum distillation.

The crude solder produced by the process according to the presentinvention is preferably further tuned for adjusting its composition andsubsequently submitted to a distillation step, preferably a vacuumdistillation step, wherein lead is removed by evaporation and a streamis remaining that is enriched in Sn. The tuning of the crude solder ispreferably performed in the way which is described in great detail inour co-pending European patent application EP-A-16190907.2, filed on 27Sep. 2016.

The applicants point out that the steps d) and m) of the processaccording to the present invention, in which the crude solder becomesavailable, are typically operated at a high temperature, typically muchhigher than 500° C., rather in the range of 700-1000° C. The applicantspoint further out that any downstream vacuum distillation for separatinglead from the solder, is typically operated at an even highertemperature. The typical temperatures for removing lead from tin byvacuum distillation are at least 900° C., often as high as 1100° C.

In an embodiment, the process according to the present invention furthercomprises the step e) of cooling the crude solder down to a temperatureof at most 825° C. to produce a bath containing a first supernatantdross which by gravity becomes floating upon a first liquid molten tunedsolder phase. Preferably the crude solder is cooled down to atemperature of at most 820° C., preferably at most 800° C., morepreferably at most 750° C., even more preferably at most 700° C., yetmore preferably at most 650° C., preferably at most 600° C., even morepreferably at most 550° C., preferably at most 525° C., more preferablyat most 500° C., even more preferably at most 450° C., preferably atmost 400° C., more preferably at most 370° C., even more preferably atmost 360° C., preferably at most 350° C., more preferably at most 345°C., even more preferably at most 330° C., preferably at most 320° C.,more preferably at most 310° C.

We have further found that when the cooling trajectory is wider and/orreaches further down in temperature, that more of these metals come outof solution and end up in the supernatant dross. The wider the coolingtrajectory is made, the more prone the cooling step becomes for beingsplit into different successive cooling steps, preferably combined withintermediate dross removal. This brings the advantage that overall lessdross may need to be removed for removing the same amount of undesiredmetals, and that the total amount of dross contains less of the targetmetals of the overall process, which are primarily lead and/or tin, butinclude also the various precious metals that may be present in thesolder and under particular circumstances also the antimony (Sb) whichmay be present. We have also found that the cooler the crude solder, thehigher its density, which is beneficial for the separation by gravity ofthe dross, because the dross comes more readily floating on top of thedenser liquid metal phase.

The applicants therefore submit that step e) of the process according tothe present invention is counter-intuitive. The applicants submit thatthe one of ordinary skill in the art would prefer to keep the solder atthe high temperature at which it was produced, possibly even heating itfurther, before it is submitted to a vacuum distillation step forseparating lead from tin. The applicants have however found that thecooling step e) of the process in accordance with the present inventionis able to move, without the intervention of any further chemicals, asignificant part of the components in the crude solder which areundesired in the feed for a vacuum distillation step, into a supernatantdross phase, this dross phase thus becoming available for beingseparated from the liquid solder phase. The applicants have found thatthis cooling step is a significant contributor in creating a separatedross phase rich in the undesired components, leaving a liquid solderphase which contains less of these undesired components and which henceis more suitable for a vacuum distillation step encountering lessoperational problems caused by the possible formation of intermetalliccompounds during the distillation step. The applicants have found thatthe cooling step is particularly capable of reducing the content ofcopper, nickel, iron and/or zinc in the remaining liquid solder phase.We have also found that the cooler the crude solder, the higher itsdensity, which is beneficial for the separation by gravity of the dross,because the dross comes more readily floating on top of the denserliquid solder phase.

In an embodiment, the process according to the present invention furthercomprises the step g) of adding an alkali metal and/or an earth alkalimetal, or a chemical compound comprising an alkali metal and/or an earthalkali metal, to the crude solder separated in step d) and/or step m) orto the first liquid molten tuned solder phase formed in step e) to forma bath containing a second supernatant dross which by gravity comesfloating on top of a second liquid molten tuned solder phase. Preferablythe step g) is operated downstream of step e), on the first liquidmolten tuned solder phase formed in that step e).

The applicants submit that step g) as part of the process in accordancewith the present invention reduces the concentration of the undesiredmetals in the liquid solder phase on its way to the vacuum distillation.This step g) however consumes chemicals, as specified. The applicantssubmit, by operating step e) and g) in series with respect to the crudesolder stream, such that the concentration of undesired metals is evenfurther reduced, that the cooling step e) brings the extra advantagethat the then subsequent chemical treatment step g) requires lesschemicals.

In an embodiment of the process according to the present invention whichincludes step g), the process further comprises the step h) of removingthe second dross from the second liquid molten tuned solder phase,thereby forming a second tuned solder.

The chemical(s) specified for step g) end up acting as a base, and thisbase ends up in the dross which may be removed downstream. The drosscontains valuable metals, and it is of economic interest to recoverthese metals from the dross phases separated from the liquid metalphases as part of the process. Many of the known recovery processes forthese metals from such dross streams are however of a pyrometallurgicalnature. They operate at very high temperatures, so high that most of theconstruction steel of the equipment which comes in contact with the hightemperature process streams, is typically protected with refractorymaterial. The chemical(s) used in step g), and ending up in the drossphase, are however aggressive towards the most typically used refractorymaterials that are used in the typical pyrometallurgical non-ferrousmetal recovery process steps. The applicants submit that the coolingstep e) therefore not only contributes in keeping down the level of thechemical(s) introduced in step g), but also contributes to the level ofacceptance for reusing the dross separated downstream of step g) inorder to recover metal values therefrom by a pyrometallurgical process.

We have found that in the cooling step e) primarily copper, zinc, ironand nickel may chemically bind with tin and that these compounds maycome floating on top provided the underlying liquid stream containssufficient lead, and thus has a sufficiently high density.

We have found that the chemical introduced in step g) is able to bindsome of the undesired metals, primarily copper and zinc, and this in aform which also readily comes floating on top as part of the secondsupernatant dross.

In an embodiment, the process according to the present inventioncomprises the step f) of removing the first supernatant dross from thefirst liquid molten tuned solder phase formed in step e), therebyforming a first tuned solder, preferably removing the first supernatantdross before operating step g), if step g) is present.

We prefer to remove the dross from each crude solder treatment stepbefore starting the subsequent treatment step. We have found that thisbrings the advantage that the overall amount of dross is smaller whencompared with the alternative of letting the dross from different stepscombine and removing all the dross together at the end of the crudesolder treatment steps. A dross contains also some tin and/or lead, andthese amounts of valuable metals are thus disadvantageously removed fromthe metal stream which is fed to the intended downstream vacuumdistillation step. These amounts of valuable metals also increase theburden of reworking the dross for recovering the metal values therein,including the entrained tin and/or lead, but also including the othermetals removed from the crude solder stream by the treatment.

In an embodiment, the process according to the present invention furthercomprises the step i) of distilling the first tuned solder from step f)or the second tuned solder from step h), whereby lead (Pb) is removedfrom the solder by evaporation and a distillation overhead product and adistillation bottom product are obtained, preferably by a vacuumdistillation.

The applicants have found that the distillation step i), downstreamfrom, or in some of the embodiments being a part of, the processaccording to the present invention, is able to operate without anyserious risk for the formation of intermetallic compounds inside thedistillation equipment.

The distillation step i) may be performed under very low pressures, suchas not more than 50 Pa absolute, possibly not more than 10-15 Pa, andoften as low as 0.1-5 Pa, in combination with relatively hightemperatures of at least 800° C., preferably at least 900° C. The vacuumdistillation of the tuned solder may be performed batch-wise, and suchbatch vacuum distillation techniques have been disclosed in CN101696475,CN104141152, CN101570826, and in Yang et al, “Recycling of metals fromwaste Sn-based alloys by vacuum separation”, Transactions of NonferrousMetals Society of China, 25 (2015), 1315-1324, Elsevier Science Press.The distillation under vacuum of the tuned solder may also be performedin continuous mode, and such continuous distillation techniques havebeen disclosed in CN102352443, CN104651626 and CN104593614. Preferablythe distillation is performed as disclosed in our co-pending Europeanpatent application EP-A-16190907.2, filed on 27 Sep. 2016.

In an embodiment of the process according to the present inventioncomprising step i), the distillation bottom product of step i) comprisesat least 0.6% wt of lead. The applicants prefer that the bottom productcomprises more than 0.60% wt of lead, preferably at least 0.65% wt oflead, more preferably at least 0.70% wt of lead, even more preferably atleast 0.75% wt of lead, preferably at least 0.80% wt of lead, preferablyat least 1.0% wt, more preferably at least 1.5% wt, even more preferablyat least 2.0% wt, preferably at least 3.0% wt, more preferably at least4.0% wt, even more preferably at least 5.0% wt, and yet more preferablyat least 6.0% wt of lead.

We believe that higher contents of Pb remaining in the bottom product ofthe distillation may act as an extra solvent, for instance for theamount of antimony, which may be present in the tuned solder. Thissolvency effect may be to the benefit of the separation in thedistillation step. The prime target of the vacuum distillation step i)is to evaporate lead (Pb) and to produce a lead-containing overheadproduct which is suitable for being cleaned up further by conventionalmeans to produce a product of high purity lead, so-called “soft-lead”.We believe that leaving an amount of lead in the bottom product of thedistillation step helps in achieving that goal, by providing a liquidphase which remains attractive for many of the metals other than lead,and hence reducing the desire of these metals to become volatile as wellas their tendency to escape from the liquid phase and to end up in theoverhead product of the distillation step. We believe that this benefitis enhanced by leaving a higher concentration of lead in the bottomproduct of the distillation step. We believe this benefit to beparticularly important for any antimony which is present in the tunedsolder according to the present invention.

We have further found that the problems of the formation ofintermetallic compounds during the vacuum distillation of the tunedsolder in step i) are further alleviated by leaving a more importantpresence of lead in the bottom product of the distillation step. Webelieve that the higher amount of lead has a beneficial impact onkeeping the potentially harmful metals better in solution and onreducing their tendency for forming the potentially disturbingintermetallic compounds during the upstream distillation step. Withoutbeing bound by theory, we believe that this effect may be based ondilution, but we suspect that there may be additional factors playing arole in reducing the risk for formation of intermetallic compounds underthe conditions occurring in the vacuum distillation step.

The bottom product can be further purified in a purifying step, whichremoves at least part of remaining contaminants such as silver, therebyforming a purified tin stream. For example, by using a technique such asis described in CN102534249, which describes a 4-step crystallizeroperation for purifying a crude tin stream by removing silver.

The lead distillate may be further purified in a purifying step, whichremoves at least part of remaining contaminants such as arsenic and tin,thereby forming a purified lead stream. For example, by using atechnique such as drossing.

In an embodiment, the process according to the present inventioncomprises the step j) of reprocessing the slag from step d) and/or stepm) in a pyrometallurgical production run or campaign for producing acopper concentrate.

With “copper concentrate” is meant a metal product comprising at least50% wt of copper, preferably at least 75% wt of copper.

The reprocessing of the slag from step d) and/or step m) may or may notbe operated in the same equipment as the process according to thepresent invention. The inventors have found that the reprocessingprovides a means for the recovery of the Sn and/or Pb which typicallyhas remained in the slag because the slag is in a phase equilibrium withthe crude solder at the moment that the two liquid phases are separatedfrom each other as part of step d) and/or step m).

In an embodiment, the process according to the present invention isoperated as a campaign, and the campaign is followed in the sameequipment by a campaign for producing a copper concentrate or a campaignfor the recovery of higher purity copper streams from a copperconcentrate, together referred to as “a copper production campaign”.

A campaign preferably comprises several consecutive batch runs having avery similar nature. The process according to the present invention ispreferably operated in consecutive cycles, whereby, after removing fromthe furnace at least a portion of the crude solder and/or of the slag,again step a) is performed by introducing again a portion of thefeedstock into the furnace and melting the added feedstock portion toagain increase the volume of the liquid bath. Subsequently, steps b) andc) and d) may be repeated. Advantageously step b) may be performed atthe same time as step a), and the reducing agent may thus be introducedtogether with the feedstock portion of step a). Also step c), ifpresent, may be performed together with step b), and optionally alsotogether with step a). The same may be performed with respect to thecorresponding steps j)-m). When the targeted reactions have sufficientlyprogressed, the separation in step d) and/or step m) may be allowed tohappen, and at least one of the liquid phases may—at least partially—beremoved from the furnace, after which again more feedstock may beintroduced into the furnace as a repeat of another step a), wherebytypically an amount of liquid has remained in the furnace when startingthe new step a). At the end of the 2 or 3 final batch runs of a crudesolder campaign, the applicants prefer to only tap crude solder and letthe slag liquid build up. A crude solder production campaign is thenpreferably finalised by feeding, melting and reacting materials that areparticularly rich in lead, and leaner in tin, as explained elsewhere inthis document. In this way, Sn is washed out from the slag phase and/orextracted from the furnace lining, and recovered in the final crudesolder from the last batch run. Preferably this “washing” with lead isrepeated several times, before the equipment is liberated for anothertype of operation, such as a copper production campaign.

The process according to the present invention preferably starts withalready a significant amount of molten metal in the furnace, as aleftover from a previous run in the same equipment. The leftover metalmay for instance be the leftover of a washing step, after a copperproduction campaign, as explained elsewhere in this document.

The applicants have found that the process according to the presentinvention is conveniently operated as one or more campaigns in equipmentwhich is also able to produce a copper concentrate containing at least70% wt and typically 75% wt of Cu, often referred to as black copper,and/or in equipment which may also be able to recover from such a copperconcentrate even higher purity copper streams, sometimes referred to asanode-type copper.

A suitable apparatus for operating a combined operation comprising thetwo different campaigns, is a smelter furnace. A smelter furnace bringsthe advantage of being relatively simple and usually represents asignificantly lower investment cost as compared to more complexalternatives. A suitable apparatus for processing a copper concentrateto recover therefrom an even higher purity copper stream is a top-blownrotary converter (TBRC).

Preferably the slag from step d) and/or step m) is reprocessed in theblack copper process or campaign, primarily for the recovery of their Snand/or Pb content, as well as for the recovery of any copper which mayfurther be present in the slag. The Sn and Pb may be recovered in a slagfrom the black copper production, and the copper may be recovered aspart of the black copper itself. Any Fe and/or SiO₂ in the slag fromstep d) and/or step m) may readily leave the process as part of the endslag from the black copper production.

In an embodiment of the process according to the present inventionoperated as a campaign and the campaign being followed in the sameequipment by a copper production, as part of the transition from thecrude solder production campaign to the copper production campaign, theequipment is subjected to at least one washing step. The washing stepbetween the two campaigns has the purpose of reducing the amount ofcross-contamination between the two campaigns, preferably reducing theamount of tin (Sn) that is lost for the crude solder production campaignand shows up as a contaminant in the copper production campaign.

The applicants prefer to perform the washing step as follows:

-   -   1) at the end of the crude solder campaign as much as possible        of the slag and of the crude solder is removed, typically        drained as liquid products, from the furnace and relevant        ancillary equipment,    -   2) lead-containing materials, preferably lead-rich materials,        are introduced into the furnace, any solids thereof are melted        in the furnace, and the liquid furnace content is agitated and        brought as much as possible in contact with the furnace inside        walls, typically represented by refractory materials, and    -   3) the molten lead is drained from the furnace and relevant        ancillary equipment.

Preferably the washing step is performed two or three times.

The applicants have found that the molten lead-containing material inthe furnace is able to extract other metals that may have becomeadsorbed in the furnace refractory lining. The liquid lead is thus ableto clean the furnace, i.e. to remove metals other than Pb that are lessdesired during a copper production campaign.

When the operations in the furnace are returned from a copper productioncampaign to a crude solder production campaign, the equipment may alsobe washed in order to reduce the amount of Cu that may still be presentin the equipment—and hence risks to end up in the crude solder—byintroducing a second washing step after as much of the copper metalphase as possible is drained. The applicants have found that such asecond washing step is less critical and may conveniently be skipped.

Preferably, such a second washing step comprises a dilution of the feedto at least one of the last copper production batches, in order to lowerthe Cu content of the copper metal phase remaining in the furnace afterdraining. The thus produced copper metal phase, depending on itscomposition, may be reprocessed in a suitable other process.Alternatively, the second washing step after a copper productioncampaign is made similar to the washing step performed after the crudesolder production campaign and comprises the feeding of Pb-richmaterials, preferably Pb scrap material, after as much as possible ofthe copper metal phase is drained from the furnace. This addition oflead-rich materials drives more of the remaining Cu present in thefurnace into the metal phase before the latter is removed. The metalphase produced from these second washing step, optionally from asequence of several thereof, comprises Cu, together with Pb and possiblysome Sn. This metal phase is tapped and, depending on its composition,is preferably reprocessed in a suitable process for valuable metalrecovery.

The inventors have found that the reprocessing of the slag from thecrude solder production campaign during the black copper productioncampaign brings the advantage that any Zn which may be present in thefeedstocks of the crude solder production campaign may end up in theslag of the black copper production campaign, and during the blackcopper campaign may be fumed out from the furnace content. The Zn maythus readily be removed from the overall process and conveniently berecovered as (ZnO) dust from the exhaust gasses. Any Cd present in thefeedstocks may also be removed from the overall process in the same wayand be collected in the dust phase as cadmium oxide together with theZnO.

In an embodiment, the process according to the present invention furthercomprises the addition in step c) and/or step l) of oxides of metalswhich are more noble than Zn, such as PbO.

The inventors have found by adding metals which are more noble than Zn,that Zn may be converted to its oxide during step c) and/or step l),which zinc oxide is then pushed into the slag. The slag from step d)and/or step m), which is comprising the ZnO, may then be reprocessed inthe black copper process or campaign, during which a significant part ofthe ZnO may be fumed out and recovered. During the fuming, the ZnO istypically first reduced to Zn which evaporates and oxidizes again incontact with the oxidizing furnace atmosphere, forming again ZnO in aparticulate form which is then evacuated with the exhaust gasses and mayreadily be recovered as ZnO dust while the remaining part of theoriginal ZnO in the liquid phase ends up in the slag from the blackcopper process or campaign. The re-oxidation of the Zn in the furnaceatmosphere generates heat, which may partially be used to heat up therefractory lining of the furnace, thereby increasing the temperature ofthe slag and increasing the removal rate of ZnO for a givenconcentration in the slag. We have found that the temperature of theslag bath to realize a convenient fuming rate is preferably at least1200° C. We have however found that the temperature should preferablynot exceed 1300° C., in order to reduce the wear of the refractorylining of the furnace.

Inevitably, the metal phase still comprises metals such as Zn and Cdwhich are considered as being contaminants in the crude solder.Therefore, Zn and Cd are preferably further removed from the metal phasein an efficient way.

In an embodiment, the process according to the present invention furthercomprises as part of step c) and/or step l) the fuming of Zn out of themetal phase in the furnace and the collection thereof as ZnO dust in thefurnace exhaust gas.

Preferably, this ZnO dust as obtained as part of step c) and/or step l)of the process according to the present invention is reprocessed in asubsequent solder composition production run, for the purpose ofrecovering the Sn present in this ZnO dust. The inventors have foundthat reprocessing the ZnO dust is more advantageous than selling thedust as such to Zn processing plants, because the dust typically alsocomprises other contaminants which may be undesirable in the downstreamZn production process. For example, the ZnO dust may comprise halogens,primarily chlorine, which preferably concentrate in this dust. Beforebeing reprocessed in a solder composition production run, at aparticular level of halogens, this dust is therefore preferably washedin order to remove halogens, in particular chlorine. Furthermore, wehave found that cadmium (Cd) tends to concentrate in this dust, and thatit is typically not washed out together with the halogens. When the Cdlevel in the ZnO dust is higher than what is acceptable in the Znproduction process, it is more advantageous to reprocess the ZnO dust byadding the dust to the liquid bath of a black copper process run, suchthat any Sn (and also Pb) which is present in this leftover ZnO dust mayat least be recovered.

The inventors have found that in order to limit the total halogencontent in the exhaust gas dust, i.e. the ZnO-containing dust, down toat most 10% wt, relative to the total dry weight of the ZnO-containingdust, the feedstock preferably comprises a limited content of halogens,primarily of CI, Br, F, more preferably of chlorine (CI).

In an embodiment of the process according to the present invention, thefeedstock to the process comprises at most 2.0% wt of halogens,preferably less than 1.5% wt. The halogens that should be limited asspecified is the total of CI, Br and F together, most preferably theprescribed limit applies to chlorine only.

The inventors have further found that halogens tend to bring othermetals than Zn in the exhaust gasses, by forming chlorides that arevolatile at the operating conditions, such as SnCl₂, and thereforecreate the risk that significant amounts of valuable metals would belost into the exhaust gas dust, which at best are reprocessed and thusrepresent a process inefficiency. Furthermore, we found that halogensalso may lead to the formation of sticky, non-permeable, exhaust dust onthe fabric of the dust filters and therefore may cause technicalproblems in the exhaust gas treatment equipment by condensing as liquidphases and subsequent solidification at cooler places.

It is understood that all definitions and preferences, as describedabove, equally apply for all further embodiments, as described below.

In an embodiment, the process according to the present invention isoperated in semi-batch mode and comprises the following steps:

j) introducing, after step d) and/or step m), at least a further portionof the feedstock into the furnace comprising a liquid bath of metalphase and/or molten metal oxide slag, thereby increasing the volume ofliquid in the furnace;

k) introducing into the furnace, as a reducing agent, material whichcontains significant, and preferably effective, amounts of the elementalform of at least one metal which is less noble than Sn and Pb,preferably of elemental Fe, Al and/or Si (alternatively called Fe, Aland/or Si metal), and by oxidation thereof reducing tin and/or leadoxides into their elemental metal form, thereby changing the compositionof the metal phase and/or the slag phase in the furnace;

l) optionally introducing into the furnace at least one energy sourcecomprising a combustible material and/or at least one metal which isless noble than Sn and Pb, and oxidizing the combustible material and/orthe at least one metal in the energy source by the injection of airand/or oxygen into the furnace;

m) separating the crude solder obtained in step k) and/or I) from theslag and removing from the furnace at least a part of the crude solderand/or of the slag; and

n) repeating the process starting from step j) or step a).

The inventors have found that the composition of the slag and/or metalphase in the furnace may be adjusted by the introduction of materialswhich contain significant amounts of the elemental form of at least onemetal which is less noble than Sn and Pb, preferably of elemental Fe, Aland/or Si metal, in order to change the distribution of the differentmetals that are present in the furnace between the slag phase and themetal phase, which may be affected by the oxidation of the less noblemetal to an oxide. The applicants have found that this reaction of theless noble metal also brings energy to the furnace content, energy thatthus does not need to be supplied by an energy source and an oxidant, aspart of step c) and/or step l).

Although a long list of metals qualify as being less noble than Sn andPb, the applicants prefer to use Fe, Al and/or Si in step k), becausethese offer the best balance of availability, reactivity andcontrollability of the energy supply into the liquid bath.

The applicants add that elemental aluminium (Al) is listed above as asuitable metal to be introduced as part of step k), but that the use ofAl in this step does introduce the same safety and industrial hygienerisks, because of the presence of antimony (Sb) and arsenic (As), ofsomewhere downstream forming the highly toxic gas stibine (SbH₃) orarsine (AsH₃), as explained above in this document in the context of the“cuprosilicon” process. The use of Al may therefore only be allowed ifaccompanied with very stringent and complex safety measures downstreamof the process according to the present invention. The applicantstherefore have found that Al is not the preferred elemental metal to beadded as part of step k), and that the preferred metals to be added instep k) are iron and silicon, with the prime advantage of avoiding thesesafety and industrial hygiene risks.

When the process according to the present invention is performed insemi-batch mode, it means that the furnace is usually not fully emptiedover an entire campaign, e.g. during a period as long as 1.5-2 years.The inventors have found that it is advantageous to maintain a minimumamount of liquid bath in the furnace, for example in a typical smelterfurnace with a total furnace content of 88 tons, a minimum amount of 55tons is preferred. The applicants prefer to leave for the subsequentprocess step a significant amount of liquid volume into the furnace,preferably at least 10% of the available furnace internal furnacevolume, more preferably at least 15% volume.

The applicants also prefer that the molten metal phase that is presentin the furnace at the start of step a) or of step j) contains at least1% wt of at least one elemental metal that is less noble than Sn and

Pb, preferably at least 2% wt, more preferably at least 3% wt, even morepreferably at least 4% wt, yet more preferably at least 5% wt. Theapplicants prefer that this minimum presence applies to the presence ofiron (Fe). This brings the advantage, upon the addition of feedstockcontaining Sn and/or Pb oxide, that the reduction of these feedstockcomponents into elemental Sn and/or Pb may start immediately upon theaddition of the respective oxide. A further advantage is that this redoxreaction is exothermic, and thus brings energy into the liquid bath,which is useful for the melting of further added feedstock, whichtypically is added as a solid, typically rather cold, if not at ambienttemperature. The presence of this selected metal, in the elemental form,in the liquid bath at the start of step a) or step j), therefore maybring significant gains in terms of batch time and/or of equipmentproductivity.

In an embodiment the process in accordance with the present inventioncomprises the introduction, as part of step c) and/or step l), of acombustible material as an extra energy source. In the presence ofsufficient oxygen, this brings the advantage of extra supplies of energyand/or reducing agent into the liquid bath. The further advantage isthat the addition of such combustible material may more readily andaccurately be controlled, as compared to the addition of the reducingagent as part of step b) or step k) and/or the energy source comprisingat least one metal which is less noble than Sn and Pb. A suitablecombustible material is for instance wood, coal, any organic liquid, anypetroleum or derivative thereof, natural gas, or a mixture of at leasttwo thereof.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, comprisesmore than 9.5% wt of tin, preferably at least 10% wt of tin, morepreferably at least 11% wt, even more preferably at least 13% wt,preferably at least 15% wt, more preferably at least 16% wt, preferablyat least 17% wt of tin, more preferably at least 18% wt, even morepreferably at least 19% wt, preferably at least 20% wt, more preferablyat least 25% wt, preferably at least 30% wt, more preferably at least32% wt, even more preferably at least 34% wt, yet even more preferablyat least 36% wt, preferably at least 38% wt more preferably at least 40%wt, even more preferably at least 42% wt of tin.

We have found that a higher amount of tin in the crude solder reducesthe melting point of the crude solder, with the advantage that thepossible downstream processes may be operable over a wider temperaturerange. We have also found that the high purity tin metal which may berecovered downstream from the crude solder according to the presentinvention typically represents a higher economical value than mostlead-rich prime products. A higher tin content in the crude solderaccording to the present invention therefore increases the economicupgrade potential of the composition.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than69% wt of tin, preferably at most 68% wt of tin, more preferably at most65% wt, preferably at most 62% wt, more preferably at most 60% wt, evenmore preferably at most 58% wt, yet even more preferably at most 57% wt,preferably at most 55% wt, more preferably at most 53% wt, even morepreferably at most 51% wt of tin.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, more than25% wt of lead, preferably at least 28% wt of lead, more preferably atleast 30% wt, even more preferably at least 32% wt, preferably at least34% wt, more preferably at least 36% wt, even more preferably at least37% wt, yet even more preferably at least 38% wt, preferably at least39% wt, more preferably at least 40% wt, even more preferably at least41% wt of lead.

We have found that a higher amount of lead in the crude solder improvesany separation steps which may be operated downstream of the stepsperformed in the furnace. We have also found that a higher lead content,thereby typically representing a lower tin content of the crude solder,brings the advantage that the solubility of copper in the crude solderis reduced. A lower copper content of the crude solder allows to morereadily obtain a lower copper content in the ultimately recoverableprime products, such as high purity tin and/or lead, for example byvacuum distillation, reducing the burden associated with the downstreamremoval of the remaining traces of copper. Furthermore, a lower coppercontent, at least above the minimum levels specified below, decreasesthe risk of forming intermetallic compounds during the vacuumdistillation.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than90% wt of lead, preferably at most 85% wt, more preferably at most 80%wt, even more preferably at most 75% wt, preferably at most 73% wt, morepreferably at most 72% wt, preferably at most 71% wt, more preferably atmost 70% wt, even more preferably at most 69% wt, yet even morepreferably at most 68% wt, preferably at most 67% wt, more preferably atmost 66% wt, even more preferably at most 65% wt, preferably at most 60%wt, more preferably at most 55% wt, even more preferably at most 50% wt,preferably at most 48% wt, more preferably at most 46% wt, even morepreferably at most 44% wt of lead.

We have found that increasing the amount of lead in the crude solderabove the specified limits does not further significantly enhance theadvantages associated elsewhere in this document with a higher amount oflead in the crude solder according to the present invention. We havefurther found that the higher amounts of lead dilute the typically morevaluable tin in the crude solder, thereby reducing the potentialeconomic value of the crude solder.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, more than80% wt of tin and lead together, preferably at least 81% wt, morepreferably at least 82% wt, preferably at least 83% wt, more preferablyat least 84% wt, even more preferably at least 85% wt, yet morepreferably at least 86% wt, preferably at least 87% wt, more preferablyat least 88% wt, even more preferably at least 89% wt, preferably atleast 89.5% wt, more preferably at least 90% wt, even more preferably atleast 90.5% wt of tin and lead together. The crude solder comprisespreferably at most 96% wt of Sn and Pb together.

The crude solder according to the present invention is of interest as afeedstock for the recovery of high purity tin and/or lead, e.g. by meansof a vacuum distillation step as part of the overall process. Primeproducts, such as tin and lead, desirably should meet as high aspossible the international trade standards which are in practice, andtherefore non-prime by-products need to be removed from the primeproducts down to a level which is imposed by the prime productspecifications. A higher content of tin and lead together increases theamount of prime products which may be recovered from the crude solder,and reduces the amount of usually lower value by-product streams whichmay emerge from the further purification steps, e.g. these forpurification of the distillation products into prime product streams.This feature also increases process efficiency and reduces the burdenassociated with the disposal and/or possible recycle of the non-primeby-product streams. This burden comprises chemicals and energyconsumption, but also manpower and equipment investment costs. Thehigher content of tin and lead together thus increases the economicinterest in the crude solder according to the present invention as afurther feedstock for recovering tin metal in high purity, as well aslead metal in economically acceptable forms.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, more than0.08% wt of copper, preferably at least 0.10% wt, more preferably atleast 0.20% wt, even more preferably at least 0.50% wt, yet morepreferably at least 0.75% wt, preferably at least 1.00% wt, morepreferably at least 1.25% wt, even more preferably at least 1.50% wt,yet even more preferably at least 1.65% wt of copper, preferably atleast 1.75% wt of copper, more preferably at least 1.85% wt, preferablyat least 1.90% wt, more preferably at least 1.95% wt, even morepreferably at least 2.0% wt, yet even more preferably at least 2.1% wt,preferably at least 2.2% wt more preferably at least 2.3% wt, even morepreferably at least 2.4% wt, preferably at least 2.5% wt more preferablyat least 3% wt, even more preferably at least 3.5% wt, preferably atleast 4.0% wt more preferably at least 4.5% wt, even more preferably atleast 5.0% wt of copper.

We have found that the above specified amounts of copper may be left inthe crude solder according to the present invention withoutsignificantly affecting the usefulness of the crude solder after tuning[tuned solder, herein after]. The crude solder after tuning may be usedas further feedstock for a vacuum distillation step withoutsignificantly reducing or destroying the effect which is obtained by thepresent invention, i.e. increasing the risk that a vacuum distillationstep performed on the tuned solder, would not anymore be able to operatein continuous mode over an extended period of time without encounteringproblems of intermetallic compounds comprising copper which impair thevacuum distillation operations. We have found that the identifiedproblems may be reduced to a practically and economically acceptablelevel when the small amounts of copper, as specified, remain present inthe crude solder according to the present invention when used aftertuning as feedstock to the vacuum distillation step.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than11% wt of copper, preferably at most 10% wt of copper, preferably atmost 9% wt, more preferably at most 8% wt, even more preferably at most7% wt, yet even more preferably at most 6% wt of copper, preferably atmost 5.5% wt, more preferably at most 5% wt, even more preferably atmost 4.5% wt of copper.

We have found that the lower the concentration of copper in the crudesolder according to the present invention, the lower the risk for theformation of intermetallic compounds when the tuned solder is subjectedto vacuum distillation. We have further found that the lower the copperpresence in the crude solder according to the present invention, thelower the concentration of copper in the product streams obtained fromthe downstream vacuum distillation. This reduces the burden associatedwith the further purification steps by removal of copper from thesestreams on their path towards becoming prime products, in particular interms of consumption of chemicals which may be used in these downstreampurification steps and in terms of amounts of by-products formed. Theseby-product streams are preferably recycled to a step upstream of theprocess in accordance with the present invention and may still comprisethe chemicals which may have been used in the purification step. Thisfeature thus also brings an advantage in terms of reducing thepotentially damaging effects of these chemicals in this recycleoperation, such as by attacking the refractory material in an upstreampyrometallurgical step.

In an embodiment, the metal mixture according to the present inventioncomprises, relative to the total weight of the crude solder, less than0.7% wt of zinc, preferably at most 0.69% wt of zinc, more preferably atmost 0.68% wt, preferably at most 0.65% wt, more preferably at most0.63% wt, even more preferably at most 0.60% wt, yet even morepreferably at most 0.580% wt, preferably at most 0.570% wt, preferablyat most 0.560% wt, preferably at most 0.550% wt, more preferably at most0.540% wt, preferably at most 0.50% wt, more preferably at most 0.40%wt, even more preferably at most 0.30% wt, yet even more preferably atmost 0.20% wt, preferably at most 0.10% wt, more preferably at most0.08% wt, even more preferably at most 0.06% wt, yet even morepreferably at most 0.05% wt of zinc.

We have found that a vacuum distillation which is performed on the crudesolder according to the present invention after tuning, i.e. the tunedsolder, may be particularly sensitive to the presence of zinc. Zinc iscapable of forming intermetallic compounds, and hence may contribute tothe problem addressed by the present invention. Zinc is also a rathervolatile metal and any zinc present may also at least partially becomepart of the vapour phase inside the distillation equipment. The heatingin the distillation equipment is very often provided electrically, bysending an electric current through heating electrodes inside thedistillation equipment. We have found that a control of the presence ofzinc within the prescribed limits reduces the risk for electric arcsthat may be pulled between two points of these heating electrodes whichmay be located close to each other and between which there is a voltagedifference. Such electric arcs represent a short in the electricalcircuit of the heating installation, and are often a cause of immediateequipment shutdown. In case of absence or malfunction of fuses, they mayeven cause damage to the transformer and AC/DC converter in theelectrical system. The electric arcs are damaging and possiblydestroying the electrodes, and may in addition also burn through thefurnace wall, in particular when drawn between an electrode and thefurnace wall.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, at least0.0001% wt of zinc, preferably at least 0.0005% wt, more preferably atleast 0.0010% wt, even more preferably at least 0.0050% wt, preferablyat least 0.010% wt, more preferably at least 0.02% wt, even morepreferably at least 0.03% wt of zinc.

We have found that it is not necessary to remove zinc down to levelsbelow the specified limits in order to sufficiently alleviate theproblems which zinc may cause during the vacuum distillation of thetuned solder according to the present invention. We have found thatsmall amounts of zinc, as specified, may therefore be left in the crudesolder which is used after tuning as feed for a vacuum distillation. Wehave found, with the zinc content being within the specified limits inthe crude solder according to the present invention, that the target lowlevels of zinc in the prime purified metal end-products may readily bereached.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than2.80% wt of nickel, preferably at most 2.755% wt of nickel, morepreferably at most 2.750% wt, preferably at most 2.745% wt, morepreferably at most 2.742% wt, even more preferably at most 2.741% wt,yet even more preferably at most 2.740% wt, preferably at most 2.730%wt, more preferably at most 2.720% wt, even more preferably at most2.710% wt, preferably at most 2.6% wt, more preferably at most 2.4% wt,even more preferably at most 2.2% wt, preferably at most 2.0% wt, morepreferably at most 1.5% wt, even more preferably at most 1.0% wt,preferably at most 0.8% wt, more preferably at most 0.75% wt, even morepreferably at most 0.7% wt of nickel.

Nickel is a metal which is present in many raw materials available forthe recovery of non-ferrous metals, in particular in secondary rawmaterials, and especially in end-of-life materials. It is thus importantin the recovery of non-ferrous metals that the process is capable ofcoping with the presence of nickel. Furthermore, the pyrometallurgicalprocesses for recovering non-ferrous metals often consume significantamounts of iron as a process chemical. It is advantageous to be able toalso cope with these kinds of process chemicals. It is also advantageousto be able to use secondary iron-containing materials for this purpose.These materials may, besides high amounts of iron, also contain minorbut significant amounts of nickel. Nickel is also a metal which may formintermetallic compounds during a downstream vacuum distillation step. Wehave found that a control within the specified limits of the amount ofnickel present in the crude solder according to the present invention isable to sufficiently reduce the risk for the formation ofnickel-containing intermetallic compounds during vacuum distillation ofthe tuned solder. We have further found that it is more advantageous tobring down the nickel content in the feedstock to the vacuumdistillation step, e.g. in the tuned solder, rather than removing largeramounts of nickel further downstream in the process. Such furtherdownstream nickel removal step is typically performed together withremoving arsenic (As) and/or antimony (Sb), and carry a risk forgenerating the very toxic gasses arsine (AsH₃) and/or stibine (SbH₃).The nickel removal upstream of the vacuum distillation, down to withinthe above specified limits, therefore also reduces the downstream riskfor the generation of toxic gasses, and thus also represents a safetyand industrial hygiene measure.

In an embodiment the metal mixture according to the present inventioncomprises, relative to the total weight of the crude solder, at least0.0005% wt of nickel, preferably at least 0.0010% wt, more preferably atleast 0.0050% wt, preferably at least 0.010% wt, more preferably atleast 0.050% wt, preferably at least 0.1% wt, more preferably at least0.2% wt, preferably at least 0.3% wt, preferably at least 0.4% wt, morepreferably at least 0.5% wt, preferably at least 0.55% wt of nickel.

We have found that it is not essential to remove nickel down to levelsbelow the specified lower limits, such as below the detection limit of0.0001% wt. We have found that a control within the specified limits ofthe amount of nickel present in the crude solder according to thepresent invention may sufficiently reduce the risk for the formation ofnickel-containing intermetallic compounds during vacuum distillation ofthe tuned solder, as well as maintaining low the safety and industrialhygiene risk associated with possible downstream generation of arsineand/or stibine gas, while avoiding extra efforts in the clean-up of thecrude solder in its preparation as feedstock for a vacuum distillation.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than5% wt of antimony (Sb), preferably at most 4.50% wt, more preferably atmost 4.00% wt, preferably at most 3.50% wt, more preferably at most3.25% wt, preferably at most 3.00% wt, more preferably at most 2.50 wt%, even more preferably at most 2.35% wt, yet even more preferably atmost 2.25% wt, preferably at most 2.15% wt, preferably at most 1.95% wt,preferably at most 1.85% wt, more preferably at most 1.75% wt, even morepreferably at most 1.65% wt, yet even more preferably at most 1.55% wtof antimony.

We have found that antimony may be allowed in the crude solder accordingto the present invention, within specific limits, without creatingproblems when the tuned solder may be used as feedstock for vacuumdistillation. We have found that it is important to keep the amount ofantimony below the specified upper limit because antimony may also atleast partially evaporate under the distillation conditions. If thelevel of antimony is higher, the amount of antimony leaving thedistillation step with the high lead-containing overhead product maybecome significant. In order to obtain the higher purity prime leadproduct in compliance with demanding industry standards, this amount ofantimony needs to be removed from this lead stream in the conventionalclean-up steps downstream of the vacuum distillation step. An amount ofantimony above the specified limit increases the burden of thesedownstream clean-up steps and increases the amount of by-product streamscontaining the antimony. Because these by-product streams may alsocontain significant amounts of lead, this lead in the by-products is notending up in the prime lead product and at least reduces theeffectiveness of the overall operation.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, more than0.15% wt of antimony (Sb), preferably at least 0.20% wt, more preferablyat least 0.25% wt, even more preferably at least 0.35% wt, preferably atleast 0.45% wt, more preferably at least 0.50% wt, even more preferablyat least 0.55% wt, yet more preferably at least 0.60% wt, preferably atleast 0.65% wt, more preferably at least 0.70% wt, preferably at least0.75% wt, more preferably at least 0.80% wt, even more preferably atleast 0.9% wt, preferably at least 1.0% wt, more preferably at least1.1% wt of antimony.

We have found that the crude solder according to the present inventionmay contain measurable, and even significant, amounts of antimony,within the specified limits, without this presence of antimony bringingsignificant impairment to a possible downstream vacuum distillation stepto which the tuned solder may be subjected. We have found that thisprovides extra freedom of operation for the feedstock. Thanks to thisallowance of an amount of antimony in the crude solder according to thepresent invention, the process according to the present invention iscapable of accepting raw materials in which a significant amount ofantimony is present. Antimony may be present in a variety of primary andsecondary feedstocks for non-ferrous metals, as well as in manyend-of-life materials. Antimony may for instance be present in leadwhich was used since Roman times for plumbing purposes. Such materialsmay now become available from the stripping of buildings, often incombination with copper, such as in waste tubing, and with tin and leadin the solder connections. Allowing an amount of antimony in the crudesolder according to the present invention, provides the capability forthe process according to the present invention to accept such mixedend-of-life materials. We have found that significant concentrations ofantimony may be allowed in the crude solder according to the presentinvention without these creating significant difficulties for thedownstream processes.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than7.5% wt of iron, preferably at most 7.00% wt of iron, more preferably atmost 6.50% wt, preferably at most 6.00% wt, more preferably at most5.50% wt, even more preferably at most 5.00% wt, yet even morepreferably at most 4.50% wt, yet more preferably at most 4.00% wt,preferably at most 3.50% wt, more preferably at most 3.00% wt, even morepreferably at most 2.50% wt, yet even more preferably at most 2.00% wtof iron.

Iron is a metal which is present in many raw materials available for therecovery of non-ferrous metals, in particular in secondary rawmaterials, and especially in end-of-life materials. Iron is also a metalwhich may be introduced into the process as a reducing agent. Iron is ametal which may form intermetallic compounds during vacuum distillation.We have found that a control, within the specified limits, of the amountof iron present in the crude solder according to the present inventionis able to sufficiently reduce the risk for the formation ofiron-containing intermetallic compounds during vacuum distillation ofthe tuned solder.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, at least0.0005% wt of iron, preferably at least 0.0010% wt, more preferably atleast 0.0050% wt, even more preferably at least 0.0100% wt, preferablyat least 0.0500% wt, more preferably at least 0.1000% wt, even morepreferably at least 0.1500% wt, preferably at least 0.2000% wt, morepreferably at least 0.5% wt, even more preferably at least 0.8% wt,preferably at least 0.9% wt, more preferably at least 1.0% wt, even morepreferably at least 1.1% wt of iron.

We have found that it is not essential to remove iron down to levelsbelow the specified limits, in particular not below the detection limitof 0.0001% wt. We have found that a control within the specified limitsof the amount of iron present in the crude solder according to thepresent invention is able to sufficiently reduce the risk for theformation of iron-containing intermetallic compounds during vacuumdistillation of the tuned solder, while avoiding unnecessary extraefforts in the clean-up of the crude solder in its preparation as feedfor a vacuum distillation step.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than1.10% wt of sulphur, preferably at most 1.09% wt of sulphur, morepreferably at most 1.08% wt, even more preferably at most 1.07% wt, yeteven more preferably at most 1.06% wt, preferably at most 1.05% wt, morepreferably at most 1.04% wt, preferably at most 1.00% wt, morepreferably at most 0.80% wt, even more preferably at most 0.70% wt,preferably at most 0.60% wt, more preferably at most 0.50% wt, even morepreferably at most 0.40% wt of sulphur.

We have found that the presence of sulphur in the crude solder accordingto the present invention may cause odour problems, and may pose aproblem of industrial hygiene, even if the crude solder has been cooledand solidified. These problems may present themselves during theoperations and during storage, but may even be more important duringmaintenance interventions. We therefore prefer to bring the levels ofsulphur in the crude solder according to the present invention down towithin the specified upper limits.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, more than0.010% wt of sulphur, preferably at least 0.020% wt, more preferably atleast 0.030% wt, even more preferably at least 0.050% wt, preferably atleast 0.100% wt of sulphur.

We have found that it is not required to bring the levels of sulphurdown to levels below the specified limits, in particular not below0.010% wt or 100 ppm wt, in order to achieve the effects which aretargeted by the control of the sulphur content.

In an embodiment the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, more than0.012% wt of bismuth, preferably at least 0.015% wt of bismuth, morepreferably at least 0.02% wt, preferably at least 0.025% wt, morepreferably at least 0.03% wt, preferably at least 0.04% wt, morepreferably at least 0.05% wt, even more preferably at least 0.06% wt,yet even more preferably at least 0.07% wt, preferably at least 0.08%wt, more preferably at least 0.09% wt of bismuth.

Optionally the crude solder comprises less than 1.5% wt of bismuth,preferably at most 1.45% wt of bismuth, preferably at most 1.40% wt,more preferably at most 1.35% wt, even more preferably at most 1.30% wt,yet even more preferably at most 1.27% wt, preferably at most 1.24% wt,more preferably at most 1.21% wt, preferably at most 1.1% wt,morepreferably at most 1.0% wt, even more preferably at most 0.9% wt,preferably at most 0.8% wt, more preferably at most 0.6% wt, even morepreferably at most 0.4% wt, preferably at most 0.2% wt, more preferablyat most 0.10% wt of bismuth.

We have found that bismuth may be relatively volatile under theconditions of the vacuum distillation step. Some of the bismuth maytherefore find its way into the prime products, from which it may thenneed to be removed in order to obtain a prime product in compliance withparticularly demanding product specifications. This downstreamcontaminant removal step typically consumes chemicals and creates aby-product stream which also contains some valuable prime product. Evenif successfully recycled, these by-product streams represent a processinefficiency which is advantageously reduced.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than3% wt of arsenic, preferably at most 2.5% wt of arsenic, more preferablyat most 1% wt, preferably at most 0.8% wt, more preferably at most 0.6%wt, even more preferably at most 0.4% wt preferably at most 0.35% wt,more preferably at most 0.3% wt, even more preferably at most 0.25% wt,preferably at most 0.2% wt, more preferably at most 0.18% wt of arsenic.

We prefer to keep the amounts of arsenic within the limits as specified.This reduces the burden for removing arsenic from any of the productstreams occurring downstream from a possible vacuum distillation step.These removal steps use chemicals and generate by-product streams whichinevitably contain also some amounts of valuable metals, such as leadand/or tin. Even if successfully recycled, these by-product streamsrepresent an overall process inefficiency, and it is advantageous toreduce them. Recycling may also bring problems caused by the otherchemicals present in these by-product streams, which may e.g. have acorrosive effect on refractory materials used in the equipment of theprocess according to the present invention, or upstream or downstreamthereof, and which are in contact with hot liquid streams.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, at least0.01% wt of arsenic, preferably at least 0.02% wt, more preferably atleast 0.025% wt, preferably at least 0.03% wt, more preferably at least0.035% wt, even more preferably at least 0.038% wt, yet even morepreferably at least 0.04% wt of arsenic.

This feature brings the advantage that feedstock materials that containsome arsenic may be accepted to a certain degree. We have found that theoverall process, including the process according to the presentinvention but also including any downstream steps for further clean-upor upstream steps, is able to cope with the amounts of arsenic asspecified. In addition, the inventors have found that some Pb and/orSn-based alloys of commercial interest readily accept As up to certainlevels without any significant problems, and that selected variants ofsuch alloys even welcome the presence of As. The crude solder as well asthe process according to the present invention is therefore prepared toaccept the presence of As in its process streams, albeit within thespecified limits.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, less than0.5% wt of aluminium, preferably at most 0.40% wt of aluminium, morepreferably at most 0.30% wt, preferably at most 0.20% wt, morepreferably at most 0.10% wt, even more preferably at most 0.05% wtpreferably at most 0.04% wt, more preferably at most 0.03% wt, even morepreferably at most 0.025% wt, preferably at most 0.02% wt, morepreferably at most 0.018% wt of aluminium.

Aluminium is a metal which is present in many raw materials availablefor the recovery of non-ferrous metals, in particular in secondary rawmaterials, and especially in end-of-life materials. Aluminium is also ametal which may be introduced into the process as a reducing agent.Aluminium is a metal which may form intermetallic compounds duringvacuum distillation. We have found that a control, within the specifiedlimits, of the amount of aluminium present in the crude solder accordingto the present invention is able to sufficiently reduce the risk for theformation of aluminium-containing intermetallic compounds during vacuumdistillation of the tuned solder. A further advantage is, particularlyif the crude solder is cooled, solidified, and transported to anotherlocation where the solder needs to be remelted into a smelter beforebeing further processed, that, upon introducing oxygen such as in thesmelter process, the aluminium readily oxidizes to aluminium oxide, andhence brings significant amounts of energy into the furnace.

In an embodiment, the crude solder according to the present inventioncomprises, relative to the total weight of the crude solder, at least0.0010% wt of aluminium, preferably at least 0.0020% wt of aluminium,more preferably at least 0.0030% wt, preferably at least 0.0040% wt,more preferably at least 0.0050% wt, even more preferably at least0.0060% wt preferably at least 0.0070% wt, more preferably at least0.0080% wt, even more preferably at least 0.0090% wt, preferably atleast 0.010% wt, more preferably at least 0.012% wt of aluminium.

We have found that it is not essential to remove aluminium down tolevels below the specified limits, in particular not below the detectionlimit of 0.0001% wt. We have found that a control within the specifiedlimits of the amount of aluminium present in the crude solder accordingto the present invention is able to sufficiently reduce the risk for theformation of aluminium-containing intermetallic compounds during vacuumdistillation of the tuned solder, while avoiding unnecessary extraefforts in the clean-up of the crude solder in its preparation as feedfor a vacuum distillation step.

In an embodiment of the present invention, at least a part of theprocess is electronically monitored and/or controlled, preferably by acomputer program. The applicants have found that the control of stepsfrom the process according to the present invention electronically,preferably by a computer program, brings the advantage of a much betterprocessing, with results that are much more predictable and which arecloser to the process targets. For instance on the basis of temperaturemeasurements, if desired also pressure and/or level measurements and/orin combination with the results of chemical analyses of samples takenfrom process streams and/or analytical results obtained on-line, thecontrol program may control the equipment relating to the supply orremoval of electrical energy, supply of heat or of a cooling medium, aflow and/or a pressure control. The applicants have found that suchmonitoring or control is particularly advantageous with steps that areoperated in continuous mode, but that it may also be advantageous withsteps that are operated in batch or semi-batch. In addition andpreferably, the monitoring results obtained during or after theperformance of steps in the process according to the present inventionare also of use for the monitoring and/or control of other steps as partof the process according to the present invention, and/or of processesthat are applied upstream or downstream of the process according to thepresent invention, as part of an overall process within which theprocess according to the present invention is only a part. Preferablythe entire overall process is electronically monitored, more preferablyby at least one computer program. Preferably the overall process iselectronically controlled as much as possible.

The applicants prefer that the computer control also provides that dataand instructions are passed on from one computer or computer program toat least one other computer or computer program or module of the samecomputer program, for the monitoring and/or control of other processes,including but not limited to the processes described in this document.

Example

The enclosed FIGURE shows a flow diagram of the process that wasoperated in this example. The compositions reported in this example areexpressed in weight units, and are expressed in accordance with thelogic expressed earlier in this document with respect to the expressionof elements in their elemental form or in their oxidized form.

For the analysis of the granulated crude solder product, the sampleswere taken and reduced by quartering. Approximately 10 kg of crudesolder granulates was melted in a small furnace. The molten metal waspoured into a mould and the solid ingot was milled to obtain smallchips. The slag that was formed in equilibrium with the crude solderproduct was ground in a disc mill and screened on a 200 micron sieve.Representative weights of each obtained fraction were weighed for thedifferent laboratory assays. The final Sn analysis was performed byclassical volumetric analysis and copper, lead, zinc, iron, nickel,antimony, bismuth, aluminium, arsenic, manganese, cobalt, molybdenum,sodium, potassium, chrome and cadmium were analysed using an InductiveCouPling Optical Emission Spectrometer (ICPOES), model OPTIMA 5300 Vfrom the Perkin Elmer company, after being dissolved by acid digestion.

In a copper smelter furnace (represented as unit 100 in the FIGURE), atthe end of a copper production campaign, was added 1 smelter washingstep during which a significant amount of lead scrap was fed to thesmelter, melted and brought in intimate contact with as much of thefurnace lining as possible, after which a portion of the slag phase anda portion of the metal phase was drained from the furnace. The metaldrained from the furnace after this lead washing step was retained asthe 1^(st) batch of crude solder production (see Table 2), and was latermixed with the crude solder produced by the subsequent batches of thesame campaign. At the end of the smelter washing step was left in thesmelter furnace an amount of about 30 metric tons of liquid metal phasecomprising about 21% wt Cu, about 36% wt Sn, about 0.4% wt Ni and about37% wt of Pb. On top of that liquid metal phase was also left acontinuous layer of about 10 metric tons of molten slag phase.

For the solder campaign, the materials with the total amounts and globalcomposition as listed in Table 1 were provided. The balance of thecompositions, relative to the metal concentrations in the table, wereprimarily oxygen bound in a metal oxide. The fresh feed part of thefeedstock contained small amounts of organic material including carbon,and to a very small extent also bound sulphur. This sulphur content isalso given as part of the compositions in Table 1.

The energy source (stream 2 in the FIGURE) contained, apart from theelements shown as part of Table 1, further essentially only Si metal.

TABLE 1 Feedstock, Energy source and Reducing Agent (wt %) ElementEnergy source Reducing % wt Feedstock Coarse Fine Agent Cu 1.7444 0.01000.02 0.5834 Sn 29.0506 0.0296 0.01 13.8088 Pb 21.8877 0.0196 0.01 0.1308Fe 2.3440 22.8172 4.10 66.7409 Zn 2.9035 0.2207 0.21 0.2273 Ni 0.02910.0100 0.01 0.7452 Sb 0.5882 0.0100 0.00 0.0118 Bi 0.0429 0.0200 0.010.0000 Al 0.1772 0.0000 0.03 0.0000 As 0.0779 0.0000 0.00 0.0417 Cd0.0143 0.0100 0.00 0.0165 Total metal 58.8599 23.1475 4.40 82.3064 Pb/Snratio 0.7534 0.6622 1.00 0.0095 S 0.3802 0.0700 0.06 0.1537 Cl 0.37650.0700 0.06 0.0859 Total mass (kg) 1687037 14146 30020 182017

In the first solder batch, an amount of 13910 kg of the feedstock andabout 500 kg of the coarse energy source were gradually introduced intothe furnace. The feedstock added at the start of this first solder batchwas from the coarse part, and had previously been sieved on a sieve withopenings of 3 mm. Only the part that was retained on the sieve was usedas the feedstock for this first batch. Also the 500 kg of energy sourcewas the result after sieving over a 3 mm opening sieve.

After a continuous layer of slag had formed in the smelter furnace,gradually 56767 kg of the feedstock and 1709 kg of the fine energysource were added in the slag phase, above the metal liquid level in thefurnace. All of these amounts were fine material, having a weightaverage particle diameter of about 2 mm, and they were graduallyinjected pneumatically about at the interface level between the metaland the slag phase.

During the batch, a mixture of oxygen and methane was injected into theliquid bath, the mixture having an O₂/CH₄ molar ratio of about 2.78.During the batch also, 800 kg of purified sand (SiO2) was graduallyadded as flux material.

At the end of the batch, 23700 kg of solder (stream 6 in the FIGURE) wastapped from the furnace and granulated to become solder shots. Afterdraining this part of the solder, about 2 metric tons of solid slagoriginating from a copper production run were added as shieldingmaterial, and subsequently, at a temperature of about 1070° C. in thefurnace, most of the slag phase was drained (as stream 5 in the FIGURE)from the smelter, granulated as a slag that was later reprocessed aspart of a copper production campaign.

At the start of the second solder batch of this campaign, the smelterfurnace contained a remaining amount of about 30 metric tons of liquidmetal having the same composition as the first solder product (see Table2), and a small continuous layer of slag on top of the metal.

Spread about equally over the 20 subsequent batches, 868710 kg of thecoarse part of the feedstock and 695391 kg of the fine part of thefeedstock were added, as well as 11946 kg of the coarse part of theenergy source and 28311 kg of the fine part of the energy source. Inaddition, 182017 kg of the reducing agent (stream 3 in the FIGURE) wereadded, as appropriate and spread over the batches of the entirecampaign. Over the different batches, about 15820 kg of sand was addedas flux material, and a total of 927100 kg of solder shots were tappedin total from the smelter furnace. Each time the slag phase was poured,about 2 metric tons of solid slag from a previous copper productioncampaign was added as shielding material before the pouring of the slagphase. The slags were poured typically at a temperature in the range of1062-1170° C., granulated and collected for reprocessing during a latercopper production campaign.

Throughout the campaign, as appropriate, a mixture of natural gas andoxygen was injected into the smelter furnace. The mixture had an O₂/CH₄molar ratio of about 2.35, with the result that the furnace atmospherewas of an oxidizing nature. The exhaust gasses from the smelter furnacewere filtered for collecting the flue dust. This flue dust (stream 4 inthe FIGURE), mainly containing zinc oxide, was re-injected into thesmelter during the same or the subsequent solder batch or campaign. Whenthe CI or Cd levels in the flue dust had reached their critical limit,the dust collected at that moment onwards during the solder campaign waskept separate and reprocessed gradually during a subsequent copperproduction campaign.

The compositions and amounts of the solder productions of the firstsolder batch, of the subsequent 20 intermediate solder batches, of thetotal crude solder production from the 21 batches together, and of thelast washing step are shown in Table 2.

TABLE 2 Crude Solder Production Element 1^(st) 20 further Sum of 21Washing (wt %) Batch Batches Batches Step Cu 21.1400 4.8361 5.2425 0.56Sn 36.1200 53.1433 52.7190 0.03 Pb 37.3300 38.0800 37.0613 98.82 Fe2.2200 1.7297 1.7419 — Zn 0.7000 0.3859 0.3938 0.02 Ni 0.3900 0.50450.5017 0.09 Sb 0.7800 0.6434 0.6468 0.06 Bi 0.2110 0.0788 0.0821 0.043 S0.2100 0.1167 0.1190 0.07 Al 0.0130 0.0130 0.0130 — As 0.2000 0.20000.2000 — Total % 99.3140 99.7315 99.7210 99.693 Total Mass (kg) 23700927100 950800 17500

At the end of each solder production batch, an amount of about 30 tonsof metal was left in the furnace, on top of which was also kept acontinuous slag layer of about 30 cm thick, representing about 15-20metric tons of slag.

After the last solder production campaign, all the solder was drainedfrom the smelter, and the smelter was subsequently cleaned in oneoperation by adding and melting an amount of Pb-rich material, typicallylead scrap, followed by intense contacting of the metal phase with thefurnace lining, draining and granulating the metal phase. The amount andcomposition of the metal phase tapped after the washing/cleaning step isalso shown in Table 2. The collected metal shots from this washing stepwere reprocessed during the next solder campaign.

The solder shots produced from the batches of the campaign weretransported to a solder processing facility, remelted, and heated up toa temperature of about 835° C. before being further cleaned (i.e.“tuned”). At the time of remelting, sufficient high purity lead wasadded to the solder such that its Sn/Pb weight ratio in the solder wasabout 30/70. The tuned solder was further processed by means of vacuumdistillation.

In a first cleaning step, the crude solder was cooled down to 334° C.,in two steps. In the first step, the crude solder was cooled to about500° C. and a first dross was removed from the surface of the moltenliquid. In the second step, the crude solder was cooled further down to334° C. and a second dross was removed from the surface of the moltenliquid. The total dross contained the majority of the copper present inthe crude solder. Also the Fe and Zn content in the solder had beenreduced by this first cleaning step. The dross was removed as aby-product and reprocessed during a copper production campaign.

In a second cleaning step, solid sodium hydroxide was added to thesolder from the first cleaning step. In this treatment step, zinc wasbound by the sodium hydroxide, presumably to form Na₂ZnO₂, and forming aseparate phase which separated as a supernatant solid from the solderand which was removed. As a result, the zinc content in the solder wasfurther decreased. The amount of sodium hydroxide was adjusted such thatthe Zn concentration in the solder decreased down to about 15 ppmweight. The dross which was formed in this step was also recycled duringa copper production campaign.

In a further cleaning step, downstream of the treatment step which isusing sodium hydroxide, an amount of elemental sulphur, representingabout 130% of stoichiometry relative to the amount of copper remainingin the solder, was added to further reduce the copper content of thesolder. As elemental sulphur was used a granulated form of sulphurobtainable from the company Zaklady Chemiczne Siarkopol in Tarnobrzeg(PL). The sulphur reacted primarily with copper to form copper sulphideswhich moved into another supernatant dross phase. This dross was removedfrom the liquid solder. Post this sulphur addition step, in a subsequentstep again an amount of sodium hydroxide was added to chemically bindany leftover traces of sulphur to form another dross. After allowingsome time for the reaction, a handful of granulated sulphur wasscattered/spread over the bath surface. The sulphur ignited and burnedany hydrogen which could have evolved from the liquid as a byproductfrom the reaction. Subsequently, a small amount of white sand wasscattered/spread over the bath in order to dry/stiffen the dross. Thetotal dross formed in this last step was again removed from the liquidmetal bath. The thus obtained cleaned solder contained only about 40 ppmwt of Cu and was further processed with vacuum distillation. The sulphurcontaining dross was reprocessed in a smelter during a copper productioncampaign, so that its valuable metal content could be valorised.

The cleaned solder was further processed using vacuum distillation, atan average temperature of 982° C. and an average absolute pressure of0.012 mbar (1.2 Pa). The vacuum distillation step produced two productstreams which were suitable for being further purified into high qualityprime products according to industry standards. On the one hand weobtained as distillate a product stream which contained mainly lead andon the other hand we obtained as the bottom product a product streamwhich contained mainly tin, together with about 1.0% wt of Pb. Thevacuum distillation was performed in continuous mode, and during a timeperiod of about three (3) years without the observation of any blockingor clogging of the distillation equipment due to the formation ofintermetallic compounds. Both product streams of the vacuum distillationstep remained during the entire time period suitable for being furtherrefined to form prime products in compliance with establishedinternational industry standards.

Having now fully described this invention, it will be appreciated bythose skilled in the art that the invention can be performed within awide range of parameters within what is claimed, without departing fromthe scope of the invention, as defined by the claims.

1. A process for producing a crude solder comprising lead (Pb) and tin(Sn) from a feedstock which comprises at least 50% wt of total metal,expressed relative to the total dry weight of the feedstock, wherein thetotal feedstock comprises the following metals, the amounts of eachmetal being expressed as the total of the metal present in the feedstockin any oxidized state and in the reduced metal form, and relative to thetotal dry weight of the feedstock: at least 2% wt and at most 71% wt oftin (Sn), at least 1.00% wt and at most 10% wt of copper (Cu), at least0.02% wt and at most 5% wt of antimony (Sb), at least 0.0004% wt and atmost 1% wt of bismuth (Bi), at most 37% wt of zinc (Zn), at most 1% wtof arsenic (As), and at most 2% wt of nickel (Ni) wherein the totalfeedstock further comprises lead (Pb) and is characterized by a Pb/Snweight ratio of at least 0.5 and at most 4.0, and wherein at least oneof tin (Sn) and lead (Pb) is at least partially present in an oxidizedvalence form, the process comprising the following steps: a) obtaining aliquid bath comprising at least one of a molten metal phase and/or amolten metal oxide slag in a furnace by introducing at least a portionof the feedstock into the furnace and melting the added feedstockportion; b) introducing at least one reducing agent into the furnace andreducing at least part of the oxidized valence form of tin and/or leadinto tin and/or lead metal; c) optionally introducing into the furnaceat least one energy source comprising at least one element selected froma combustible material, at least one metal which is less noble than Snand Pb, and combinations thereof, and oxidizing the combustible materialand/or the at least one metal in the energy source by the injection ofair and/or oxygen into the furnace; separating the crude solder obtainedin step b) and/or c) from the slag and removing from the furnace atleast a portion of the crude solder and/or of the slag.
 2. The processaccording to claim 1, wherein the feedstock comprises, relative to thetotal dry weight of the feedstock, at least 51% wt of total metal. 3.The process according to claim 1, wherein the feedstock furthercomprises substances or components selected from O and S atoms, e.g.when contained in oxides and/or sulphides, any of the halogens, carbon,and organic material.
 4. The process according to claim 1, wherein thefeedstock comprises, relative to the total dry weight of the feedstock,at least 4% wt of tin.
 5. The process according to claim 1, wherein thefeedstock comprises, relative to the total dry weight of the feedstock,at most 69% wt of tin.
 6. The process according to claim 1, wherein thefeedstock comprises, relative to the total dry weight of the feedstock,at least 1.02% wt of copper.
 7. The process according to claim 1,wherein the feedstock comprises, relative to the total dry weight of thefeedstock, at most 9% wt of copper.
 8. The process according to claim 1,wherein the feedstock comprises, relative to the total dry weight of thefeedstock, at least 0.05% wt of antimony.
 9. The process according toclaim 1, wherein the feedstock comprises, relative to the total dryweight of the feedstock, at most 4% wt of antimony.
 10. The processaccording to claim 1, wherein the feedstock comprises, relative to thetotal dry weight of the feedstock, at least 0.0005% wt of bismuth. 11.The process according to claim 1, wherein the feedstock comprises,relative to the total dry weight of the feedstock, at most 0.8% wt ofbismuth.
 12. The process according to claim 1, wherein the feedstockcomprises, relative to the total dry weight of the feedstock, at most0.8% wt of arsenic.
 13. The process according to claim 1, wherein thefeedstock comprises, relative to the total dry weight of the feedstock,at most 1.7% wt of nickel.
 14. The process according to claim 1, whereinthe feedstock comprises, relative to the total dry weight of thefeedstock, at least 8% wt of lead.
 15. The process according to claim 1,wherein the feedstock comprises, relative to the total dry weight of thefeedstock, at most 80% wt of lead.
 16. The process according to claim 1,wherein the total feedstock is characterized by a Pb/Sn weight ratio ofat least 0.52 and at most 3.5.
 17. The process according to claim 1,wherein the process is operated in semi-batch mode and further comprisesthe following steps: j) introducing, after step d), at least a portionof the feedstock into the furnace which comprises a liquid bath ofmolten metal phase and/or molten metal oxide slag, thereby increasingthe volume of liquid in the furnace; k) introducing into the furnace asa reducing agent material which contains effective amounts of theelemental form of at least one metal which is less noble than Sn and Pb,and by oxidation thereof reducing tin and/or lead oxides into theirelemental metal form, thereby changing the composition of the metalphase and/or the slag phase in the furnace; l) optionally introducinginto the furnace at least one energy source comprising at least oneelement selected from the group consisting of a combustible material andat least one metal which is less noble than Sn and Pb, and oxidizing thecombustible material and/or the at least one metal in the energy sourceby the injection of at least one compound selected from the groupconsisting of air and oxygen into the furnace; m) separating the crudesolder obtained in step k) and/or l) from the slag and removing from thefurnace at least a part of the crude solder and/or of the slag; and n)repeating the process starting from a step selected from step j) andstep a).
 18. The process according to claim 1, wherein the processfurther comprises the step of the introduction, as part of step c), of acombustible material as an extra energy source.
 19. The processaccording to claim 1, wherein step a) further comprises the addition oflead into the furnace.
 20. The process according to claim 1, wherein thefurnace as used in step a) and/or step j) of the process according tothe present invention, is a smelter.
 21. The process according to claim1, wherein the portion of the feedstock used in step a) comprisesdivided solid material and comprises at most 5% wt of particles whichpass through a sieve having a sieve opening of 2.0 mm, also known as aMesh 9 sieve.
 22. The process according to claim 1, further comprisingthe step of injecting, into the liquid bath that has been formed in atleast one step selected from step a) and step j), a finely dividedportion of the feedstock, the finely divided feedstock portion having anaverage particle size of at most 10 mm.
 23. The process according toclaim 22, wherein the finely divided feedstock portion material isinjected into the liquid slag phase and above the metal phase of theliquid bath.
 24. The process according to claim 22, wherein the finelydivided feedstock portion material has an average particle size of atmost 3.36 mm.
 25. The process according to claim 1, wherein the liquidbath of molten metal that is obtained in at least one step selected fromstep a) and step j) is kept at a temperature of at least 975° C.
 26. Theprocess according to claim 1, wherein the liquid bath of molten metalthat is obtained in at least one step selected from step a) and step j)is kept at a temperature of at most 1360° C.
 27. The process accordingto claim 1, wherein the at least one reducing agent as used in at leastone step selected from step b) and step k) comprises at most 25% wt ofcopper.
 28. The process according to claim 1, wherein the at least onereducing agent as used in at least one step selected from step b) andstep k) comprises a secondary feedstock rich in Fe.
 29. The processaccording to claim 1, wherein the at least one reducing agent as used inat least one step selected from step b) and step k) further comprises ametal-containing sand.
 30. The process according to claim 1, wherein atleast one step selected from step c) and step l) is present.
 31. Theprocess according to claim 1, wherein the energy source of at least onestep selected from step c) and step l) comprises at least one metalwhich is less noble than Sn and Pb, and further comprises the injectionof at least one compound selected from air and oxygen into the liquidbath.
 32. The process according to claim 1, wherein in at least one stepselected from step d) and step m) the removal from the furnace of thecrude solder and/or the slag is performed by tapping the crude solderand/or the slag as a liquid from the furnace.
 33. The process accordingto claim 32, further comprising the step of cooling/solidifying thetapped crude solder by contacting the tapped crude solder with water toobtain crude solder granulates.
 34. The process according to claim 1,further comprising the step of recovering metal values from the slagfrom at least one step selected from step d) and step m).
 35. Theprocess according to claim 1, wherein at least one step selected fromstep d) and step m) further comprises, prior to the separation of theslag and the crude solder and to the removal of at least a portion ofthe slag, the addition to the furnace of an amount of inert solidparticulate material.
 36. The process according to claim 1, wherein atleast one step selected from step d) and step m) further comprises,prior to the separation of the slag and the crude solder, the additionof a flux material comprising SiO₂.
 37. The process according to claim 1in which the slag from at least one step selected from step d) and stepm) is reprocessed in a pyrometallurgical production campaign forproducing a copper concentrate.
 38. The process according to claim 1which is operated as a campaign, and wherein the campaign is followed inthe same equipment by a campaign for producing a copper concentrate or acampaign for the recovery of higher purity copper streams from a copperconcentrate, together referred to as “a copper production campaign”. 39.The process according to claim 38, whereby, as part of the transitionfrom the crude solder production campaign to the copper productioncampaign, the equipment is subjected to at least one washing step. 40.The process according to claim 1, further comprising the addition in atleast one step selected from step c) and step l) of oxides of metalswhich are more noble than Zn.
 41. The process according to claim 40,further comprising as part of at least one step selected from step c)and step l) the fuming of Zn out from the metal phase in the furnace andthe collection thereof as ZnO dust in the furnace exhaust gas.
 42. Theprocess according to claim 1, wherein the feedstock comprises at most2.0% wt of halogens.
 43. The process according to claim 1 for theproduction of a tuned solder from the crude solder, further comprisingthe step e) of cooling the crude solder down to a temperature of at most825° C. to produce a bath containing a first supernatant dross which bygravity becomes floating upon a first liquid molten tuned solder phase.44. The process according to 43, further comprising the step g) ofadding a compound selected from the group consisting of an alkali metaland an earth alkali metal, and a chemical compound comprising a metalselected from an alkali metal and an earth alkali metal, to the firstliquid molten tuned solder phase to form a bath containing a secondsupernatant dross which by gravity comes floating on top of a secondliquid molten tuned solder phase.
 45. The process according to claim 44,further comprising the step h) of removing the second supernatant drossfrom the second liquid molten tuned solder phase, thereby forming asecond tuned solder.
 46. The process according to claim 43, furthercomprising the step f) of removing the first supernatant dross from thefirst liquid molten tuned solder phase formed in step e), therebyforming a first tuned solder.
 47. The process according to claim 46 forfurther processing the tuned solder, further comprising step i) ofdistilling the first tuned solder from step f), wherein lead (Pb) isremoved from the solder by evaporation and a distillation overheadproduct and a distillation bottom product are obtained.
 48. The processaccording to claim 47, wherein the distillation bottom product of stepi) comprises at least 0.6% wt of lead.
 49. (canceled)
 50. A crude solderobtainable by the process according to claim 1, comprising, in additionto unavoidable impurities and relative to the total dry weight of thecrude solder: at least 9.5% wt and at most 69% wt of tin (Sn), at least25% wt of lead (Pb), at least 80% wt of tin (Sn) and lead (Pb) together,at least 0.08% wt and at most 12% wt of copper (Cu), at least 0.15% wtand at most 7% wt of antimony (Sb), at least 0.012% wt and at most 1.5%wt of bismuth (Bi), at least 0.010% wt and at most 1.1% wt of sulphur(S), at most 3% wt of arsenic (As), at most 2.8% wt of nickel (Ni), atmost 0.7% wt of zinc (Zn), at most 7.5% wt of iron (Fe), at most 0.5% wtof aluminium (Al).
 51. The crude solder according to claim 50 comprisingat least 10% wt of tin.
 52. The crude solder according to claim 50comprising at most 68% wt of tin.
 53. The crude solder according toclaim 50 comprising at least 28% wt of lead.
 54. The crude solderaccording to claim 50 comprising less than 90% wt of lead.
 55. The crudesolder according to claim 50 comprising at least 81% wt of tin and leadtogether.
 56. The crude solder according to claim 50 comprising at least0.10% wt of copper.
 57. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at most10% wt of copper.
 58. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at most0.69% wt of zinc.
 59. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at least0.0001% wt of zinc.
 60. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder at most2.755% wt of nickel
 61. The crude solder according to claim 50comprising, relative to the total weight of the crude solder, at least0.0005% wt of nickel.
 62. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at most4.50% wt antimony.
 63. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at least0.20% wt of antimony.
 64. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at most7.00% wt of iron.
 65. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at least0.0005% wt of iron.
 66. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at most1.09% wt of sulphur.
 67. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at least0.020% wt of sulphur.
 68. The crude solder according to claim 50,comprising, relative to the total weight of the crude solder, at least0.015% wt of bismuth and at most 1.45% wt of bismuth.
 69. The crudesolder according to claim 50, comprising, relative to the total weightof the crude solder, at most 2.5% wt of arsenic.
 70. The crude solderaccording to claim 50, comprising, relative to the total weight of thecrude solder, at least 0.01% wt of arsenic.
 71. The crude solderaccording to claim 50, comprising, relative to the total weight of thecrude solder, at most 0.40% wt of aluminium.
 72. The crude solderaccording to claim 50, comprising, relative to the total weight of thecrude solder, at least 0.0010% wt of aluminium.
 73. The processaccording to claim 45 for further processing the tuned solder, furthercomprising step i) of distilling the second tuned solder from step h),wherein lead (Pb) is removed from the solder by evaporation and adistillation overhead product and a distillation bottom product areobtained.